Energy from the human body may only generate small amounts of electricity but scientists think that is potentially enough for a large range of uses.
At universities around the world clothes are being tested as electricity generators, either by their movement or the temperature of the body.
For example, a vest could potentially power medical sensors that relay wirelessly blood pressure and other symptoms back to a doctor or hospital.
Making the clothing truly responsive to body movement is a challenge. Others are working on knee brackets to allow power generation as soldiers march or run.
Scientists are also using piezoelectric devices to generate power from the bounce of a rucksack.
Even buildings that consume power could one day take monitoring feed-back directly from the humans inside and cut the bill.