iPhone 3GS
Here you can find all the information you need about the iPhone 3GS.

The abbreviation 3GS stands for third generation speed. The iPhone 3GS is the successor of the iPhone 3G. The iPhone 3GS looks exactly the same as the iPhone 3G. The only differences between the 3G and the 3Gs are the improved resolution of the camera (2Mp to 3Mp), video capability, a built in compass, voice controll, support for 7,2 Mbit/s HSPDA downloading and of course the speed. The iPhone 3GS also has a built in magneto-meter to measure magnetic fields.