Over at Make: Japan, Hideo Tamura found this water-based touchscreen project, Minamo, by Taichi Inoue. It uses a tank of water, light, webcam, and LCD to create a pretty simple touch input device:
It is difficult to say that the interface of mechanical materials like a keyboard, a mouse and so on is very suitable for man. So I made the Minamo interface. “Minamo” means “Surface of water” in Japanese. Water is the most intimate material for human body. And I decided to make a touch screen interface on water surface.