How many are using their iphones for GPS Navigation in the car? I am planning on upgrading to the new iphone whenever it is released, and I am also considering purchasing a GPS unit for my car. I have not used an iphone with GPS (mine is a 2G) and I do not know what is available as far as apps to turn my iphone into a functional GPS unit with turn by turn directions and everything. What I am wondering is if it is possible to really use the iPhone as my everyday gps unit, and if it will function as well as a dedicated unit. Should I have both, or would it be redundant? What are the best apps for turn by turn GPS function, and about what is the average cost... Thanks for any help!