I bet you thought the built-in compass on your Android phone was only useful for map applications, right? Well, the developer of Metal Detector has put this hardware feature to good use for another thing - finding metal!
That's right, amazingly, the magnetic field detection properties of the in-built compass can be harnessed to sense if their is metal around. Metal Detector provides a simple and fun way to do this. Simply turn the program on, and it will start scanning for signals. The closer it gets to some metal the higher the meter will read. If it reaches the top of the bar, it'll confirm that metal has indeed been detected. There's a calibration feature built into Metal Detector that lets you adjust the sensitivity.
There are a number of settings you can play around with that make Metal Detector even more fun to use. For instance, you can set the phone to vibrate or play a sound (of your choosing) when it's found metal, and even alter the text that displays when the app is scanning or finding metal. For instance you could prank your iPhone-using pals by changing the text to say 'Detecting crap phones'. When Metal Detector is passed by the iPhone and picks up the signal it could say something like 'You should get an Android'.
Metal Detector is not a gimmick, in the sense that it can actually detect metallic objects using your phone's sensor. However, it's not the most accurate or practical way of finding metal. If you use it near a magnetic field (i.e. sat near your computer), the app can get confused and the results are not reliable. Also, bear in mind that the detector isn't particularly strong, so you need to move your phone right next to the metallic object, which kind of defeats the object of a metal detector.
If you're looking for buried treasure on the beach, Metal Detector will be pretty useless. However, it is good fun to use and great for impressing people with the powers of your Android phone.