Convert your iPhone 3G S into a Metal Detector*!
Many metals contain oxides (like magnetite or lodestone) which can cause measurable variations in the readings of a magnetic compass.
This application uses information obtained from the iPhone's compass to estimate the strength of the observed magnetic field, and then detects increases in strength that occur when the iPhone is placed near a ferromagnetic metal (like steel or iron).
* This application is presented for educational and entertainment purposes only. This is not a professional metal detector and it will only detect ferromagnetic metals (like steel or iron) when they are present in sufficient quantities.
NOTE: THIS APPLICATION REQUIRES THE USE OF A COMPASS AND IS THEREFORE ONLY COMPATIBLE WITH THE NEW IPHONE 3G S.