Compatible with iOS 8 only
Also available, Call on GV (iOS 6 & 7)
Call on GV is a Cydia substrate extension to integrate calling via Google Voice into native Phone app. The extension also works when calls are made from outside the Phone app (for example, from a website). It may not work with other Cydia extensions like Call Bar.
Call on GV supports:
Three calling mechanisms (in addition to the default carrier calling):
1) Direct dial via a GV access number (requires carrier calling plan)
2) Offline dialing (requires carrier calling plan)
3) Callback (only mechanism that may be used without calling plan by using a VOIP callback number)
This tweak is tested and supported on multiple versions of iPhones (only the callback calling method can be used without a cell service).
It is likely not to work on iPods and iPads (as it modifies the Mobile Phone app) and hence not supported.
Call on GV requires a RESPRING after installation or update. So, respring your device before you do anything.
If you already have version 3.3-1 setup to work for Direct dial you are done.Otherwise, follow the complete instructions on the support thread.
Please read the support thread for setup instructions and a description of the complete feature set.