This is a really interesting project that uses an AVR micro-controller to create a 1-key keyboard. I can think of a thousand uses for this type of device.

The idea for a 1-key keyboard comes from the need as an interaction designer to make “cheap, quick and dirty prototypes.” When creating a quick screen-based demo in e.g. Adobe Flash, a common way of quickly prototyping physical actions is to assign actions to certain key presses on a keyboard. In more advanced prototypes, physical hacks to the circuit board from a keyboard are also often used to interface custom buttons and switches with a computer.

More about making The 1-key-keyboard project [About Microcontrollers]

In the Maker Shed:
Arduino Mini Board, fully assembled