The Jail Breakers have a ton of SIP apps working across 3G that are only supposed to work across WiFi, I bet they'll figure out a way to make this one work too.
Which SIP apps work on 3G. I had only heard of hacked version of fring..but that never seems to work.
Siphon. I use it to connect to our work PBX all the time across 3G.
