Make/modify VoIP applications to work better on Tor

Depending on how hard it will be to make Tor handle VoIP applications people already want to use (#5699 (moved)), we should explore how much mileage we can get out of making our own or modifying existing VoIP applications to work better on Tor. One example here is Roger's "push to talk" not-actually-realtime-but-close VoIP wishlist item that Nathan is working on.