Perpetua, a company that specializes in renewable energy solutions for wireless sensors, is marketing an insertable chip that converts body heat into electric energy:

Known as TEGwear™ Technology, the chip uses thermoelectric energy to convert the difference between body heat and the coolness surrounding the device into usable energy. The equipment is able to produce microwatts (one-millionth of a watt) or nearly a milliwatt (one thousandth of a watt) of power, which is enough to run ultra-low power devices such as a heart rate monitor.

According to the company’s marketing VP Jerry Wiant, they're currently looking for product development partners to develop battery-free medical, fitness and safety gear worn on the body. The hardware can be easily integrated into lightweight, ultra-low power gadgets, similar to the ones exercise buffs are already using.

If all goes accordingly, the company hopes to install these chips into fitness watches, strap-on sensors and on-body pedometers by 2014.