Instead of digesting the turkey (which I didn't eat), I spent some time trying to come up with something that sets pidgin's "now playing" bit. Since the code is most likely called from a music player, I decided to do it over DBus instead of as a plugin. Fighting through the status API was not really a pleasant task, a couple patches and more than "some" time later, I was able to come up with this. It requires the unreleased pidgin 2.3.1, which likely will only support XMPP out of the box. MSNP14 also supports broadcasting current media, so it's an option for those of you who are brave enough to use it.
It's funny how many things broke in 2.3.0 because of a single patch that I applied.