diff --git a/DEVELOPER.txt b/DEVELOPER.txt
index 8467838..2d7f3b0 100644
--- a/DEVELOPER.txt
+++ b/DEVELOPER.txt
@@ -244,3 +244,23 @@ function comment_activity_objects_alter(&$token_objects, $activity_type) {
     }
   }
 }
+---------------------------------------------
+hook_activity_message_deleted($aids)
+  This hook is called after one or more activity messages is deleted. It gives
+	modules the opportunity to do things with the AIDs of the records that were
+	just removed. For example, if external caching is used for activity this
+	could be implemented to flush the cache.
+
+	Parameters
+	  $aids - An array of activity IDs
+
+Example:
+/**
+ * Implementation of hook_activity_message_deleted().
+ */
+function mymodule_activity_message_deleted($aids) {
+  foreach ($aids as $aid) {
+		$cachekey = 'activity::' . $aid;
+    cache_clear_all($cachekey, 'cache');
+	}
+}
diff --git a/activity.module b/activity.module
index 2d632ca..a59e905 100644
--- a/activity.module
+++ b/activity.module
@@ -805,6 +805,9 @@ function activity_delete($aids) {
            INNER JOIN {activity_messages} m ON m.amid = at.amid
            WHERE a.aid IN (" . db_placeholders($aids) . ")", $aids
   );
+
+  // After the activity is deleted, another module might want the aids
+  module_invoke_all('activity_message_deleted', $aids);
 }
 
 /**