http://blog.makezine.com/2012/10/29/magnetic-appcessories-with-andrea-bianchi/
Tangible interface designer and inventor Andrea Bianchi, along with his colleague, Ian Oakley (University of Madeira / Carnegie Mellon Europe), have come with a novel approach to interacting with a mobile device. Using the magnetometer built into most modern smartphones, Bianchi and Oakley have created a series of tangible user interface demonstrations that go beyond what’s achievable with capacitive touch displays.