How much power could I extract from body heat using a TEC? I don't need much(just powering some LEDs).

What is a TEC? Depending on how that works, I might be able to assist.

It's basically an arrangement of thermocouples. They use a difference in temperature to generate a voltage.

I think the human body puts out about 100 watts in heat energy YodaP.

Probably not that much then, do you know how many volts per degrees the TEC can produce? It doesn't seem like you would be able to produce enough from using body heat, due to heat transfer from you to the metal.

 

You most likely would not be relying on just what the body can generate directly, so the way the device works will greatly effect what you can get. Just because you convert your temperature into energy via KT or of the like, it is somewhat arbitrary until it is applied to something.