Just wondering if I could make some suggestions:

Allow multiple numbers to be set as the screenname? I like to use skype for my calls, but send texts straight from my phone, and the SMS option with GV isn't there when skype is set as my forwarding number (since I don't have SMS enabled for it in google voice). Being able to at least set one number for texts and one for calls would be good.

And would it be possible to make an offline mode? I believe you can call into google voice, and then dial a contact's number from there, perhaps there could be a way for TOR to call your Google Voice number, and then input a contact's number.