Icelandic micromusic artist CombatDave hacked this together with a Wii Guitar Hero controller, an imported Game Boy Light, music programmer/sequencer LSDJ, and Arduinoboy for MIDI-to-Game Boy communication. Dave explains the setup's technical advantages, beyond rocking out to Tetris tracks:

"Basically, the beauty of this approach is I can tailor exactly what gets output by which combinations of buttons, including chords, etc. At the moment it's set up for a minor scale, and in chord mode it plays powerchords. Also, the - button sends a midi CC which controlled the decay of the guitar synth in Ableton to allow for palm muting. The vast majority of these features could only be done in something such as Processing or (maybe) max/msp."

Here's a clip showing all the pieces that make this possible, as well as another short but wicked performance: