PiPlay is just awesome. We've seen many custom joystick builds so we were inspired to create one as well - but without any physical buttons. We used our dev-kit called Hover (www.justhover.com) and paired it with an Arduino and Raspberry Pi to create a gesture controller: http://www.justhover.com/retro-gestures

For the games with simpler controls, it works great and makes them a lot more challenging. At the moment, we support swiping gestures in the air (up/down/left/right) and also touch input on five pads on the board.

Let me know what you guys think!