Here is a cool little arm on wheels I bought from ServoCity, its called the Stacker. I ordered the Stacker and the stronger lift and grip servo but not the wheel servos, EZ-B servos work just fine. I can lift a full 12oz beer with these servos with a little rubber tape on the gripper so the beer does not slip. The compartment under the arm holds the EZ-B and battery pack just fine. Also its made from 1/4" ABS so it can be drilled to hold other accessories like the camera, sonar etc.
Here is the link to the Stacker.