Getting Warmer: Using Heat to Guide via GPS

German and Swedish researchers strapped a Peltier device to a woman's elbow, connected it to a GPS unit, and then used five different levels of heat to play a real-life game of "Hotter, Colder." Don't expect this in real phones, well, ever.

The team also suggest other ways of using heat - to signal the importance of incoming calls:
"While your boss or your girlfriend will let the phone heat up remarkably, the device will stay cool when your mother tries to call during a meeting."

GPS phone guides by playing 'hotter, colder' [New Scientist via Gizmodo]