Hi!
I found this link: http://aqualords.kaj84.net. Seems to work reasonly well and you don't have to leave your key open on a pulic site.
If I understood correctly the list will be updated so that only people that actually has used Oneswarm during the lasted 14 days is included. That should significally increase the possibility to get friends that actually has you in there lists. You need to add the list on a regular basis to get the users that are currently active.
Try is out.
If you know more services of this kind please post it in this thread with a short description of how it works.