diff --git a/livesync/indico_livesync/cli.py b/livesync/indico_livesync/cli.py
index c6b8296..1b0d1d5 100644
--- a/livesync/indico_livesync/cli.py
+++ b/livesync/indico_livesync/cli.py
@@ -75,3 +75,37 @@ def initial_export(agent_id, force=False):
     print 'TODO: run initial export'
     agent.initial_data_exported = True
     db.session.commit()
+
+
+@cli_manager.command
+def create_agent(agent_type, name=None):
+    """Creates a new agent"""
+    update_session_options(db)
+    try:
+        agent_class = current_plugin.agent_classes[agent_type]
+    except KeyError:
+        print 'No such agent type'
+        return
+    # TODO: Prompt for agent type specific settings
+    agent = LiveSyncAgent(backend_name=agent_type, name=name or agent_class.title)
+    db.session.add(agent)
+    db.session.commit()
+    print agent
+
+
+# TODO: delete_agent, update_agent, create_task
+
+
+@cli_manager.command
+def run(agent_id=None):
+    if agent_id is None:
+        agents = LiveSyncAgent.find_all()
+    else:
+        agent = LiveSyncAgent.find_first(id=int(agent_id))
+        if agent is None:
+            print 'No such agent'
+            return
+        agents = [agent]
+
+    for agent in agents:
+        pass  # TODO
diff --git a/livesync/indico_livesync/handler.py b/livesync/indico_livesync/handler.py
new file mode 100644
index 0000000..7b029bd
--- /dev/null
+++ b/livesync/indico_livesync/handler.py
@@ -0,0 +1,155 @@
+# This file is part of Indico.
+# Copyright (C) 2002 - 2014 European Organization for Nuclear Research (CERN).
+#
+# Indico is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation; either version 3 of the
+# License, or (at your option) any later version.
+#
+# Indico is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Indico; if not, see <http://www.gnu.org/licenses/>.
+
+from __future__ import unicode_literals
+
+from collections import defaultdict
+
+from flask import g
+
+from indico.core import signals
+from MaKaC.accessControl import AccessController
+from MaKaC.conference import Conference, Contribution, SubContribution, Category, Session
+
+from indico_livesync.models.queue import LiveSyncQueueEntry, ChangeType
+from indico_livesync.util import obj_ref
+
+
+class LiveSyncSignalHandler(object):
+    def __init__(self, plugin):
+        # request
+        plugin.connect(signals.after_process, self._apply_changes)
+        plugin.connect(signals.before_retry, self._clear_changes)
+        # moved
+        plugin.connect(signals.category_moved, self._moved)
+        plugin.connect(signals.event_moved, self._moved)
+        # created
+        plugin.connect(signals.category_created, self._created)
+        plugin.connect(signals.event_created, self._created)
+        plugin.connect(signals.contribution_created, self._created)
+        plugin.connect(signals.subcontribution_created, self._created)
+        # deleted
+        plugin.connect(signals.category_deleted, self._deleted)
+        plugin.connect(signals.event_deleted, self._deleted)
+        plugin.connect(signals.contribution_deleted, self._deleted)
+        plugin.connect(signals.subcontribution_deleted, self._deleted)
+        # title
+        plugin.connect(signals.category_title_changed, self._title_changed)
+        plugin.connect(signals.event_data_changed, self._title_changed)
+        plugin.connect(signals.contribution_title_changed, self._title_changed)
+        plugin.connect(signals.subcontribution_title_changed, self._title_changed)
+        # data
+        plugin.connect(signals.category_data_changed, self._data_changed)
+        plugin.connect(signals.event_data_changed, self._data_changed)
+        plugin.connect(signals.contribution_data_changed, self._data_changed)
+        plugin.connect(signals.subcontribution_data_changed, self._data_changed)
+        # protection
+        plugin.connect(signals.category_protection_changed, self._protection_changed)
+        plugin.connect(signals.event_protection_changed, self._protection_changed)
+        plugin.connect(signals.contribution_protection_changed, self._protection_changed)
+        # ACLs
+        plugin.connect(signals.access_granted, self._acl_changed)
+        plugin.connect(signals.access_revoked, self._acl_changed)
+        plugin.connect(signals.modification_granted, self._acl_changed)
+        plugin.connect(signals.modification_revoked, self._acl_changed)
+        # domain access
+        plugin.connect(signals.category_domain_access_granted, self._domain_changed)
+        plugin.connect(signals.category_domain_access_revoked, self._domain_changed)
+        plugin.connect(signals.event_domain_access_granted, self._domain_changed)
+        plugin.connect(signals.event_domain_access_revoked, self._domain_changed)
+
+    def _moved(self, obj, old_parent, new_parent, **kwargs):
+        print '_moved', obj, old_parent, new_parent
+        self.register_change(obj, 'moved')
+        category_protection = old_parent.isProtected()
+        new_category_protection = new_parent.isProtected()
+
+        if category_protection != new_category_protection and obj.getAccessProtectionLevel() == 0:
+            self.register_change(obj, ChangeType.protection_changed)
+
+    def _created(self, obj, parent, **kwargs):
+        print '_created', obj, parent
+        self.register_change(parent, ChangeType.data_changed)
+        self.register_change(obj, ChangeType.created)
+
+    def _deleted(self, obj, **kwargs):
+        print '_deleted', obj, kwargs
+        parent = kwargs.pop('parent', None)
+        self.register_deletion(obj, parent)
+
+    def _title_changed(self, obj, **kwargs):
+        if kwargs.pop('attr', 'title') != 'title':
+            return
+        print '_title_changed', obj, kwargs
+        self.register_change(obj, ChangeType.title_changed)
+
+    def _data_changed(self, obj, **kwargs):
+        print '_data_changed', obj, kwargs
+        self.register_change(obj, ChangeType.data_changed)
+
+    def _protection_changed(self, obj, old, new, **kwargs):
+        print '_protection_changed', obj, old, new
+        if new == 0:  # inheriting
+            new = 1 if obj.isProtected() else -1
+        if old != new:
+            self.register_change(obj, ChangeType.protection_changed)
+
+    def _acl_changed(self, obj, principal, **kwargs):
+        print '_acl_changed', obj, principal
+        self._handle_acl_change(obj)
+
+    def _handle_acl_change(self, obj, child=False):
+        if isinstance(obj, (Conference, Contribution, SubContribution, Category)):
+            # if it was a child, emit data_changed instead
+            if child:
+                self.register_change(obj, ChangeType.data_changed)
+            else:
+                self.register_change(obj, ChangeType.protection_changed)
+        elif isinstance(obj, Session):
+            owner = obj.getOwner()
+            if owner:
+                self.register_change(owner, ChangeType.data_changed)
+        elif isinstance(obj, AccessController):
+            self._handle_acl_change(obj.getOwner(), child=False)
+        else:
+            self._handle_acl_change(obj.getOwner(), child=True)
+
+    def _domain_changed(self, obj, **kwargs):
+        print '_domain_changed', obj
+        self.register_change(obj, ChangeType.protection_changed)
+
+    def register_deletion(self, obj, parent):
+        self.init_livesync_g()
+        g.livesync[obj_ref(obj, parent)].add(ChangeType.deleted)
+
+    def register_change(self, obj, action):
+        self.init_livesync_g()
+        g.livesync[obj_ref(obj)].add(action)
+
+    def init_livesync_g(self):
+        if not hasattr(g, 'livesync'):
+            g.livesync = defaultdict(set)
+
+    def _apply_changes(self, sender, **kwargs):
+        if not hasattr(g, 'livesync'):
+            return
+        for ref, changes in g.livesync.iteritems():
+            LiveSyncQueueEntry.create(changes, ref)
+
+    def _clear_changes(self, sender, **kwargs):
+        if not hasattr(g, 'livesync'):
+            return
+        del g.livesync
diff --git a/livesync/indico_livesync/migrations/201410311223_1c2b0e17447d_create_tables.py b/livesync/indico_livesync/migrations/201410311223_1c2b0e17447d_create_tables.py
index 17c9386..4b2662f 100644
--- a/livesync/indico_livesync/migrations/201410311223_1c2b0e17447d_create_tables.py
+++ b/livesync/indico_livesync/migrations/201410311223_1c2b0e17447d_create_tables.py
@@ -32,9 +32,13 @@ def upgrade():
                     sa.Column('id', sa.Integer(), nullable=False),
                     sa.Column('agent_id', sa.Integer(), nullable=False, index=True),
                     sa.Column('timestamp', UTCDateTime(), nullable=False),
-                    sa.Column('change', sa.String(), nullable=False),
-                    sa.Column('data', postgresql.JSON(), nullable=False),
+                    sa.Column('change', sa.SmallInteger(), nullable=False),
+                    sa.Column('category_id', sa.String()),
+                    sa.Column('event_id', sa.String()),
+                    sa.Column('contrib_id', sa.String()),
+                    sa.Column('subcontrib_id', sa.String()),
                     sa.ForeignKeyConstraint(['agent_id'], ['plugin_livesync.agents.id']),
+                    sa.CheckConstraint('change IN (1, 2, 3, 4, 5, 6)'),
                     sa.PrimaryKeyConstraint('id'),
                     schema='plugin_livesync')
 
diff --git a/livesync/indico_livesync/models/queue.py b/livesync/indico_livesync/models/queue.py
index b511896..89451b8 100644
--- a/livesync/indico_livesync/models/queue.py
+++ b/livesync/indico_livesync/models/queue.py
@@ -16,18 +16,27 @@
 
 from __future__ import unicode_literals
 
-from sqlalchemy.dialects.postgresql import JSON
-
 from indico.core.db.sqlalchemy import db, UTCDateTime
 from indico.util.date_time import now_utc
 from indico.util.string import return_ascii
+from indico.util.struct.enum import IndicoEnum
 
 from indico_livesync.models.agents import LiveSyncAgent
 
 
+class ChangeType(int, IndicoEnum):
+    created = 1
+    deleted = 2
+    moved = 3
+    data_changed = 4
+    title_changed = 5
+    protection_changed = 6
+
+
 class LiveSyncQueueEntry(db.Model):
     __tablename__ = 'queues'
-    __table_args__ = {'schema': 'plugin_livesync'}
+    __table_args__ = (db.CheckConstraint('change IN ({})'.format(', '.join(map(str, ChangeType)))),
+                      {'schema': 'plugin_livesync'})
 
     #: Entry ID
     id = db.Column(
@@ -39,6 +48,7 @@ class LiveSyncQueueEntry(db.Model):
     agent_id = db.Column(
         db.Integer,
         db.ForeignKey('plugin_livesync.agents.id'),
+        nullable=False,
         index=True
     )
 
@@ -49,18 +59,34 @@ class LiveSyncQueueEntry(db.Model):
         default=now_utc
     )
 
-    # XXX: maybe use an Enum for this?
-    # XXX: or should it be an array? old code seems to have records with multiple changes
-    #: the change type
+    #: the change type, a :class:`ChangeType`
     change = db.Column(
-        db.String,
+        db.SmallInteger,
         nullable=False
     )
 
-    #: Data related to the change
-    data = db.Column(
-        JSON,
-        nullable=False,
+    #: The ID of the changed category
+    category_id = db.Column(
+        db.String,
+        nullable=True
+    )
+
+    #: The event ID of the changed event/contribution/subcontribution
+    event_id = db.Column(
+        db.String,
+        nullable=True
+    )
+
+    #: The contribution ID of the changed contribution/subcontribution
+    contrib_id = db.Column(
+        db.String,
+        nullable=True
+    )
+
+    #: The subcontribution ID of the changed subcontribution
+    subcontrib_id = db.Column(
+        db.String,
+        nullable=True
     )
 
     #: The associated :class:LiveSyncAgent
@@ -71,15 +97,22 @@ class LiveSyncQueueEntry(db.Model):
 
     @return_ascii
     def __repr__(self):
-        return '<LiveSyncQueueEntry({}, {}, {}, {})>'.format(self.agent, self.id, self.change, self.data)
+        return '<LiveSyncQueueEntry({}, {}, {}, {})>'.format(self.agent, self.id, ChangeType(self.change).name,
+                                                             self.data)
 
     @classmethod
-    def create(cls, change, data):
+    def create(cls, changes, obj_ref):
         """Creates a new change in all queues
 
-        :param change: the change type
-        :param data: the associated data (a json-serializable object)
+        :param changes: the change types, an iterable containing
+                        :class:`ChangeType`
+        :param obj_ref: the object reference (returned by `obj_ref`)
+                        of the changed object
         """
+        obj_ref = dict(obj_ref)
+        obj_ref.pop('type')
         for agent in LiveSyncAgent.find():
-            db.session.add(cls(agent=agent, change=change, data=data))
+            for change in changes:
+                entry = cls(agent=agent, change=change, **obj_ref)
+                db.session.add(entry)
         db.session.flush()
diff --git a/livesync/indico_livesync/plugin.py b/livesync/indico_livesync/plugin.py
index bd6eebc..0cad969 100644
--- a/livesync/indico_livesync/plugin.py
+++ b/livesync/indico_livesync/plugin.py
@@ -19,6 +19,7 @@ from __future__ import unicode_literals
 from indico.core.plugins import IndicoPlugin, wrap_cli_manager
 
 from indico_livesync.cli import cli_manager
+from indico_livesync.handler import LiveSyncSignalHandler
 
 
 class LiveSyncPlugin(IndicoPlugin):
@@ -31,8 +32,8 @@ class LiveSyncPlugin(IndicoPlugin):
 
     def init(self):
         super(LiveSyncPlugin, self).init()
-        # noinspection PyAttributeOutsideInit
         self.agent_classes = {}
+        self.signal_handler = LiveSyncSignalHandler(self)
 
     def add_cli_command(self, manager):
         manager.add_command('livesync', wrap_cli_manager(cli_manager, self))
diff --git a/livesync/indico_livesync/util.py b/livesync/indico_livesync/util.py
new file mode 100644
index 0000000..cc13d58
--- /dev/null
+++ b/livesync/indico_livesync/util.py
@@ -0,0 +1,57 @@
+# This file is part of Indico.
+# Copyright (C) 2002 - 2014 European Organization for Nuclear Research (CERN).
+#
+# Indico is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation; either version 3 of the
+# License, or (at your option) any later version.
+#
+# Indico is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Indico; if not, see <http://www.gnu.org/licenses/>.
+
+from __future__ import unicode_literals
+
+from MaKaC.conference import Conference, Contribution, SubContribution, Category, CategoryManager, ConferenceHolder
+from werkzeug.datastructures import ImmutableDict
+
+
+def obj_ref(obj, parent=None):
+    """Returns a tuple identifying a category/event/contrib/subcontrib"""
+    if isinstance(obj, Category):
+        ref = {'type': 'category', 'category_id': obj.id}
+    elif isinstance(obj, Conference):
+        ref = {'type': 'event', 'event_id': obj.id}
+    elif isinstance(obj, Contribution):
+        event = parent or obj.getConference().id
+        ref = {'type': 'contribution', 'event_id': event, 'contrib_id': obj.id}
+    elif isinstance(obj, SubContribution):
+        contrib = parent or obj.getContribution()
+        ref = {'type': 'subcontribution',
+               'event_id': contrib.getConference().id, 'contrib_id': contrib.id, 'subcontrib_id': obj.id}
+    else:
+        raise ValueError('Unexpected object: {}'.format(obj.__class__.__name__))
+    return ImmutableDict(ref)
+
+
+def obj_deref(ref):
+    """Returns the object identified by `ref`"""
+    if ref['type'] == 'category':
+        try:
+            return CategoryManager().getById(ref['category_id'])
+        except KeyError:
+            return None
+    elif ref['type'] in {'event', 'contribution', 'subcontribution'}:
+        event = ConferenceHolder().getById(ref['event_id'], quiet=True)
+        if ref['type'] == 'event' or not event:
+            return event
+        contrib = event.getContributionById(ref['contrib_id'])
+        if ref['type'] == 'contribution' or not contrib:
+            return contrib
+        return contrib.getSubContributionById(ref['subcontrib_id'])
+    else:
+        raise ValueError('Unexpected object type: {}'.format(ref['type']))