iPhone 3GS is a metal detector.

On the beach with your family, or just walking around town? You probably could use some extra cash. Whip out that iPhone 3GS and see if you can track down some metal.

With this handy little app released by GP Imports, 3GS owners can use the phone’s internal compass to sense strong magnetic fields (other than the north pole), thus pointing to metals. The app allows you to see how strong a magnetic field actually is and adjust the sensitivity of your detector, so you won’t get stuck digging for mere chump change.

The app costs $0.99 and is available for download at the iTunes Store.