diff --git a/ext/README b/ext/README
index 744310a0..1ad802eb 100644
--- a/ext/README
+++ b/ext/README
@@ -7,6 +7,5 @@ debug.py
   and will likely be removed before release.
 
 on-modify.timewarrior
-  This is hook script that will integrate Taskwarrior and Timewarrior.
-
+  This is a Taskwarrior hook script that will integrate Timewarrior.
 
diff --git a/ext/on-modify.timewarrior b/ext/on-modify.timewarrior
index aec16c65..385ed875 100755
--- a/ext/on-modify.timewarrior
+++ b/ext/on-modify.timewarrior
@@ -1,8 +1,33 @@
 #!/usr/bin/env python
+################################################################################
+#
+# Copyright 2015 - 2016, Paul Beckingham, Federico Hernandez.
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+#
+# http://www.opensource.org/licenses/mit-license.php
+#
+################################################################################
 
 import sys
-
-# This is a placeholder for a Taskwarrior hook script that integrates Timewarrior
+import json
+import os
 
 # Hook should extract all of the following for use as Timewarrior tags:
 #   UUID
@@ -11,5 +36,27 @@ import sys
 #   Description
 #   UDAs
 
-sys.exit(0)
+# Make no changes to the task, simply observe.
+old = json.loads(sys.stdin.readline())
+new = json.loads(sys.stdin.readline())
+print(json.dumps(new))
+
+# Extract attributes for use as tags.
+tags = [new['uuid'], new['description']]
+
+if 'project' in new:
+  tags.append(new['project'])
+
+if 'tags' in new:
+  tags.extend(new['tags'])
+
+combined = ' '.join(['"%s"' % tag for tag in tags])
+
+# Started task.
+if 'start' in new and not 'start' in old:
+  os.system('timew start ' + combined)
+
+# Stopped task.
+elif not 'start' in new and 'start' in old:
+  os.system('timew stop ' + combined)