Funny timing, see the thread directly above this one!
(
http://groups.google.com/group/wimas3/t/48997903a8d069da )
It will likely be basically identical to regular IMs, you can actually
already see most of the frame for using them in the current version
anyway if you want to have a sniff around. (session.sendDataIM, and
the dataIM object/event)
If you're interested in a patch to have them working, it may not be
final yet but I've linked my current implementation in that post, feel
free to give it a try.