The PrintBot RHINO is an educational robot that can push objects with its dozer and take part in "sumobots fights".  You can see it in action at : http://youtu.be/r0RgC5rzKug  The robot has been designed to attach components such as servos, LEDs, push buttons, a buzzer, and other electronics parts.  RhinoBot can be controlled via bluetooth using an android app or also, can operate autonomously.