I've created a serial command firmware for the Rainbowduino, based on the Rainbow_CMD_2.0 sketch. It's been refactored, performance has been improved, and I've added some additional functionality. I will post a Python module for accessing it later. For the usual reasons, it's currently restricted to controlling a single Rainbowduino, but I am thinking about extending it to handling a set of connected ones.
http://dl.getdropbox.com/u/1115694/RainbowCmdSerial.zip
Feel free to contact me if you have issues or questions. Thanks to the team at Seeed labs for excellent hardware, and some really useful software.