VoiceCentral / GV Mobile

VoiceCentral and Google Voice Mobile were two iPhone applications that tapped into Google's Voice service, including its dialer, user SMS, and voicemail system. Both apps were yanked in late July as part of Apple's mass removal of Google Voice-specific apps.
 
GV Mobile lives on though. Developer Sean Kovacs re-released the application on Cydia, a third-party application directory and installer for jailbroken iPhones and iPods. VoiceCentral, however, is still at the whim of Apple as to whether it will ever return to the App Store.

The good news for both apps is that they could one day return. That is if this whole Google vs. AT&T vs. Apple hate triangle resolves itself.