Canonical's Launchpad has a really handy feature where you can associate a bug with another on an external tracker. The status of the bug is reflected on the local bug. You can see this feature in action [[ https://bugs.launchpad.net/ubuntu/+source/abiword/+bug/948128 | here ]]. With more info on 'bug watches' on the [[ http://blog.launchpad.net/bug-tracking/launchpads-bug-watch-system-and-other-animals | Launchpad blog ]] and [[ https://wiki.ubuntu.com/Bugs/Watches | Ubuntu wiki ]]. Changes to the remote bug are reflected locally. This is really handy for a number of workflows, particularly when a product or projects involves third party open-source libraries and bugs are found. I propose that Phabricator's Maniphest would benefit from this functionality.