A heat powered electrical device that comprises - a Thermo Electric Generator adapted to harness heat and convert the heat to electrical energy; and - an energy harvesting system connected to the Thermo Electric Generator and adapted to process the harnessed electrical energy in order to power a load, wherein the energy harvesting system comprises a low power energy harvesting circuit and a high power energy harvesting circuit, characterized In that - the heat powered electrical device is a body heat powered wireless transmitter comprising a wireless transmitter, wherein the Thermo Electric Generator harnesses a user's body heat such as, tor example, heat from the user's hand, wrist or palm, and converts the body heat to electrical energy which is supplied to the low power energy harvesting circuit and to the high power energy harvesting circuit, - wherein the low power energy harvesting circuit comprises one or more step up transformers forming an oscillator which is operated in resonance mode, - the high power energy harvesting circuit comprising one or more Enhancement Mode Metal Oxide Semiconductor Field Effect Transistors that have an RDSon of 0.1 ohms or less, - wherein the low power energy harvesting circuit is adapted to operate at a power level that is at least ten times lower than the high power energy harvesting circuit, - the low power energy harvesting circuit power output powers the gate of the Enhancement Mode Metal Oxide Semiconductor Field Effect Transistor of the high power energy harvesting circuit, thereby driving or triggering the high power energy harvesting circuit to deliver the electrical energy as output power to the wireless transmitter, - whereby the device is able to operate with 20mV DC or less generated by the Thermo electric generator from the user's body heat, and - the output of the high-power energy harvesting circuit powers the wireless transmitter from the user's body heat to send data via RF, InfraRed, Ultrasonic or via another transmission medium. - a Thermo Electric Generator adapted to harness heat and convert the heat to electrical energy; and - an energy harvesting system connected to the Thermo Electric Generator and adapted to process the harnessed electrical energy in order to power a load, wherein the energy harvesting system comprises a low power energy harvesting circuit and a high power energy harvesting circuit, characterized In that - the heat powered electrical device is a body heat powered wireless transmitter comprising a wireless transmitter, wherein the Thermo Electric Generator harnesses a user's body heat such as, tor example, heat from the user's hand, wrist or palm, and converts the body heat to electrical energy which is supplied to the low power energy harvesting circuit and to the high power energy harvesting circuit, - wherein the low power energy harvesting circuit comprises one or more step up transformers forming an oscillator which is operated in resonance mode, - the high power energy harvesting circuit comprising one or more Enhancement Mode Metal Oxide Semiconductor Field Effect Transistors that have an RDSon of 0.1 ohms or less, - wherein the low power energy harvesting circuit is adapted to operate at a power level that is at least ten times lower than the high power energy harvesting circuit, - the low power energy harvesting circuit power output powers the gate of the Enhancement Mode Metal Oxide Semiconductor Field Effect Transistor of the high power energy harvesting circuit, thereby driving or triggering the high power energy harvesting circuit to deliver the electrical energy as output power to the wireless transmitter, - whereby the device is able to operate with 20mV DC or less generated by the Thermo electric generator from the user's body heat, and - the output of the high-power energy harvesting circuit powers the wireless transmitter from the user's body heat to send data via RF, InfraRed, Ultrasonic or via another transmission medium.