Metal Detector HD Prank

Use your phones built-in magnetics sensor to detect metals that distort the natural magnetic field.Technically speaking only metals that contain ferrimagnetic elements such as iron, nickel and cobalt will register variations onscreen.
When a ferrimagnetic metal object obscures the natural magnetic field and the result is shown realtime on the graph. Different shapes and sizes of metal contain ferrimagnetic elements will all register in a different ways; long thin items like screwdrivers seem to have to greatest effect so have fun experimenting!