This looks like an interesting project made with an Arduino and a laser pulled from a laser level. There are schematics and a video on the website if you want to try and make one for yourself.
After programming the Arduino, I took out the ATMega168 and wired it into a breadboard along with a 16mhz crystal and 5 volt regulator. For the receiver I used the phototransistor wired into two logic gates of a inverting Hex Schmitt trigger. I used the Schmitt trigger to act as a buffer and ensure only proper logic level enter the USB to serial converter on the Diecimila board.
Read more about how to make a Laser Modem with an Arduino Micro-controller
