Touch Board is an innovative Arduino-based project that can turn any conductive material into a capacitative touch input using electrically conductive paint.
Perhaps the most stunning example of the Touch Board's capability was a piano setup the company created at Maker Faire. Miniature piano keys were painted onto a flat surface and connected -- via electrically conductive paint -- to the Touch Board, with each 'note' on the piano connected to a different input. The board is then pre-programmed to play a different sound for each input when triggered. Developers Bare Conductive have even developed an incredible paint-on DJ kit using the Touch Board.
The Touch Board can be embedded with 'distance code' that makes it sensitive enough that it can be interacted with from up to 20 cm away.