Edison ...
check out this thread:
http://forum.ppcgeeks.com/showthread.php?t=53866
I've had Gizmo voip working on 21501 but have not had success on newer 6.5 builds. The newer HTC phones like the TP don't have the earpiece / rear speaker issue but I've never found a fix for the xv6700 or xv6800.
cya