Some sort of simplified HTTP streaming interface.
rcoaster would first serve up a pls file, with repeat turned on, that has URLs in it something like:
http://somehost.running.rcoaster:1234/currentSong

The port in that URL would be listened to by rcoaster, and rcoaster would stream out the raw mp3 file of whatever is
currently playing.  This way, rcoaster doesn't need to know anything about the file format.
Pausing may be able to be accomplished by stopping the relay.  Because of caching in xmms/winamp, pausing would be delayed,
probably.
Next-song, prev-song, etc, could probably be accomplished by just closing the socket, so that xmms/winamp are forced
to reconnect, and get whatever song rcoaster then serves up.