Ok I set the sipgate caller ID to block (not sure if that's right). Anyway, I found the setting on sipdroid to use 3G. Tested it and was able to connect to a call. However the delay was about 3 seconds on a full strength 3G connection. Also the volume on the handset uses media volume and having it up all the way is still too low. Not looking good for this being a Vonage replacement for me. Maybe Gizmo5 will be a lot better. May be just ok in the meantime over fast wifi.
Speaking of Vonage, they have an app for iphone, but I didn't post that here I will start a new thread if there isn't one yet.