March 28, 2013: Following the successful dual HBridge integration, I added the Bluetooth UART module, and wrote a software for Android OS, to allow me to control the robot by using the phone. Here's a demo video:

And a few pictures to show the final robot shape:

Next thing to do is to make the robot follow the user, AUTOMATICALLY! I'm currently considering two options, one involves using the GPS Module, send the coordinates via bluetooth to user's mobile phone that also has GPS and can then inform the robot where it needs to go, the second option would be to use some kind of beacons, the user would carry in his/her hand (or pocket), and the robot would detect those and follow the signal.