Index: relativity.module
===================================================================
--- relativity.module	(revision 557)
+++ relativity.module	(working copy)
@@ -212,6 +212,13 @@
     $child  = node_load($child_nid);
     if (relativity_may_unchild($parent, $child)) {
       $result = db_query('DELETE FROM {relativity} WHERE nid = %d AND parent_nid = %d', $child_nid, $parent_nid);
+
+      // Allow modules to act on a detach.
+      foreach (module_implements('relativity_detach') as $module) {
+        $function = $module . '_relativity_detach';
+        $function($parent, $child);
+      }
+
       drupal_set_message(t('Node relationship removed.'));
     }
     else {