Is it possible to getUserMedia... take the stream and process it with Web Audio API to run it through some filters and then send the processed audio to a peer using WebRTC?
I have been scouring the web for such examples. I found plenty that use Web Audio API after receiving a peer's stream but none processing the audio before sending it to a peer. Also no definitive statements that says it is, or is not, possible.
Check out http://simpl.info/webrtcwebaudio. That sample generates a sound and passes it to a peer; you should be able to get a source from getUserMedia in the normal way (a la http://webaudiodemos.appspot.com/input/index.html) and hook it into Web Audio.