Nokia Game Center Pad transforms your Lumia 820 in a full game console with 8 programmable buttons, d-pad, analog stick and rear touch panel.
Game Center use Bluetooth 3.0 to connect with your cellphone and have a wireless rechargeable battery, so you can charge your cellphone and your game pad at the same time.
Part of the GrabCAD and NOKIA contest.
http://grabcad.com/library/nokia-game-center-lumia-820 (http://grabcad.com/library/nokia-game-center-lumia-820)
I model this in Rhino and all the renders (of course) in Keyshot 4 ;)