[Lain Sharp] modified this guitar tuner so it can be used by his blind friend. In the picture above you can make out a small white project box that houses the additional electronics. Inside is another battery and an ATmega168 providing a connection for an earphone. The AVR chip connects to each LED on the tuner and converts the visual tuning meter to an audio cue. Check out the demonstration clip after the break to see how it works.
Now if we could just figure out how to get our strings in tune with our built-in keyboard.