This acoustic piezzo trigger to serial interface is indeed pretty ghetto, but never to less there is plenty of great information on NoisyBox.net about programming a Pic Microcontroller for building such a device.The creator decided to use strait serial protocol for triggering samples through a custom application running on a PC and not through standard MIDI. Also housing projects in an external drive case does have advantages. Its cheap, rugged, and has a nice power supply built-in, so the circuit does not have to rely on battery power. The cases can always be painted if needed.