Vippie supposedly supports the right video codecs (h.263 & h.264) but it doesn't support dialing off-network SIP addresses (which is a bit poor).
I've got all the codecs enabled in my 2Talk settings so that _should_ be ok.
Ideally I'm trying to get my Galaxy Tab to be able to dial in to our Tandberg system. I can get it working fine audio-only using the native SIP support in Android 2.3, but I've yet to have any joy with video.
Has anyone had any success with SIP video & Android?