I'm planning on getting an iPhone, but I have a few questions that I need to resolve for purchasing one. (Probably waiting for the iPhone 5, but the questions should be universal for any recent iPhone.) How does the iPhone GPS system work? Can it be used without a wireless and cellular signal? (I presume that GPS function works within the Maps application as the iPhone has a GPS chip.) Does it mean I can pinpoint my location on the globe in a region without any signal?