Why not just buy a Scribber from Parallax?:

The Scribbler is a great robot, and we do encourage folks to purchase them as an introductory robot. If you like the Scribbler, and you want to step up in functionality, you can then purchase our IPRE Fluke add on board. The add on board provides:

• Bluetooth connectivity between your computer and robot;
• Color vision;
• Access to Myro software that runs on your desktop or laptop computer. This allows you to program the robot in Python.

The IPRE kit includes a Scribbler, the IPRE Fluke add on board, Myro software CD and a digital version of our textbook.