I have an extra iPhone 3G and currently its serving no purpose. I have a window mount for the iPhone, but don't want to take the case off of my 3GS to put it in the mount. Then it hit me, could I use my old 3G without a SIM, toss Navigon on it, throw it in the window mount, and use that as a GPS? Would this work? I could then just leave my old 3G in the car as a dedicated GPS. Any thoughts?