Jailbreakers have altered most of the functionality on the iPhone except one . . . the phone app itself. Outside of skinning the phone app with winter board, it amazes me that no one has altered the way this app functions so that we could have the tight integration with google voice that Android has. It would be great if you guys could make a paid app that allows Google voice caller ID calls with the native phone app.
I would assume this could be accomplish one of two ways: 1. By calling the user's google voice number and adding the pauses and key combination necessary to complete the outgoing call (i.e. 818-MYG-VNUM########2 818-NUM-2CAL). Or 2. Using the direct dial method that your black swan app uses where the phone could discretely call the GV access number without user intervention.
Please consider my suggestion because this would really ease Google Voice use on the iPhone. Apple has made this more complicated than it should be and I'm certain you guys would make boatloads of money if you invested the time to make this happen.