I think this problem apply to many who try to take advantage of google voice's free calling with gizmo5. Here is the situation: I have a tmobile prepaid number (bound to my n900 sim card) and a gizmo5 account. I usually give out my google voice's number only to others. I also do not want to miss any calls when people calling my google voice's number. So in my google voice account, I set "phones to ring" to both my tmobile prepaid, and gizmo5. This way, when i am connected to wifi, I can use n900's native SIP support to receive google voice calls (and make calls using the one ring or dialcentral). And when I not connected to wifi, I can still use my tmobile prepaid as a backup to answer any incoming calls.

The problem with this setup is, when I am connected to Wifi, google voice will ring both my tmobile and my gizmo/sip account. This creates two rings on my n900, and usually tmobile comes about a second early. Since tmobile prepaid is not free, i have to make sure that I am answering the SIP call and reject the tmobile. Sometimes, when I take the SIP call, the tmobile ring is still ringing, creating a mess.

Is there any way that I can have google voice to ring phones one by one rather than all at same time? Or simply, is there any apps that I can set google voice not to ring my tmobile when my gizmo/sip account is registered?