This is a Robot car which can be controlled using any mobile phone. This was a project I did years ago, while learning digital electronics in the college. It was a time when I knew only less about microcontroller programming else almost the whole circuit could be replaced by a small microcontroller. The  mobile phone is placed inside the car. To control the car, just call that mobile phone  in the car after enabling the DTMF keypad tones in the calling phone. Then press 2 to move forward, 8 for backward, 2/4 for left/right control.The following video shows it in action although it is not controlled by another phone in the video.