iPhone developer & hackers thezimm & InfectionFX are working on a tweak that will bring turn by turn navigation to iPhone Map App & clubbed with VoiceActivator.
There is no info about price or release date available at the moment, but here is demo video of turn by turn navigation tweak for iPhone.
I didn’t see any demo of turn-by-turn navigation in that video. Yes, it calculated directions from one point to another. How amazing. Ho-hum.