Want to create a custom input device for your computer, that you can use to control an existing program? Then you might want to check out the Teensy, which is a USB development board that can emulate a human input device (HID) such as a mouse or keyboard. The folks over at How To Get What You Want took things a step further, and created a Sewable Fabric Breakout to make it easy to connect the Teensy up to a soft circuit creation. Instructions and a template are available at their site.
Making a soft-circuit input device for your computer