Cool project. I recently did a similar project that involved controlling an Arduino from Node.JS. A friend suggested I use Firmata, which is a standard protocol for talking to Arduinos via the serial port.
http://firmata.org/wiki/Main_Page
Very painless to use, and the script for the Arduino is included on the Aruidino SDK examples menu. You can get up and running in Node.JS in just a few lines of code.
For what it's worth, my project involved playing the brass bells on a christmas ornament from a game of 2048.