Nastypixel is a design collective, composed of people associated with Interaction Ivrea in Italy. As a contribution to open-source learning, they have published a a series of excellent step-by-step tutorials, or “recipes”, on how to make various DIY interactive projects. The first project, Soundpad, teaches you how to take apart a computer keyboard and appropriate the internal logic to your own needs. This way you can connect four button pads to your computer, where a Flash software component plays different sounds depending on the pad you press.
As a note on gestural interfaces, previously mentioned on Intwo, SmartRetina is a platform for computer gesture recognition, developed by Yaniv Steiner of Nastypixel. It has a camera component and a software component, forming the base for touchless gestural interfaces.