The motion feedback MP3 player is a concept that aims to encourage a higher level of activity during a workout, where it relies on a SparkFun MP3 Trigger , Parallax PIR Motion Sensor , and an ioBridge IO-204 Controller. Whenever the PIR sensor detects any motion, the IO-204 will send serial commands to the MP3 player in order to raise or lower the volume. Apart from that, the IO-204 controller also enables one to data log any activity whenever it is connected to the Internet. You know Newton and his laws – a body in motion stays in motion, and this MP3 player concept plays on that premise.