What an amazing idea! I can already see clothes with embedded hundreds of Peltier TE junctions in it... As a matter of fact, I WANT to create mine right now!
A prototype wearable device I designed and made for charging handheld devices, smart watches, phones, video game devices, etc, using electricity harvested from body heat. Thermoelectricity produced from bismuth-selenide peltier elements by the Seebeck effect produces a low voltage and a more or less stable current when a constant temperature differential is created across the element. This can be accomplished by having a constant heat source and a constant heat sink, i.e. a cooling apparatus. The low voltage can be boosted using a standard low voltage boosting circuit which boosts the voltage from millivolts to around 5V-9V.
This is a more ethical way to convert someone from a human into this:
After all, we humans dump a lot of energy in the form of heat. As micro-power technology increases, this energy will become more and more effective into powering electronic devices. Watch the following video and get some ideas!