Metal Detector for 3GS/4
Install "Metal Detector" on your iPhone 3GS, start the application, calibrate the detector and move your iPhone near to an object. The spire oscillates, the diode lights up and your iPhone beeps : you are closed to a metallic source !
An application only available for iPhone 3GS, you will make a lot of jealous people.
Choose your favorite option : beeper, vibrator, both or mute mode.