Body Sensors Use Gathered Power

Another example of the use of body gathered power.

Sticker sensor monitors your body using wireless power
It wouldn't interfere with your behavior.

Jon Fingas, @jonfingas in Engadget

Wearable body sensors have a common problem: they need power and antennas, and all that equipment leads to bulky devices that influence your behavior. Stanford researchers, however, have developed a system that could be almost imperceptible. Their BodyNet sticker sensor gathers power and transmits data using an RFID connection to a receiver on nearby clothing, making the sensor itself about as comfortable and flexible as an adhesive bandage. It measures subtle changes in skin that provide a wealth of data for the body, whether it's your heartbeat, breathing rate or muscle activity.  .... "