Thermoelectric Energy Harvesting
The problem is way more than just "the current".

Before you start this project, look up something called the Carnot efficiency.  That's a bit of basic physics that tells you the maximum efficiency you can get power from a temperature difference with.

Let's say the body temperature is 37 &deg;C and the room is 21 &deg;C.  That's about 310 &deg;K and 294 &deg;K.  Even a ideal heat engine can only extract about 5% of the available power.  Maybe you can actually realize 1%.  Now figure a human runs at about 50 W (being generous) just sitting around at 21 &deg;C.  That means you'd get 500 mW if every last bit of heat from the human went thru your converters before being released into the room.

Unless you are prepared for miniscule amounts of power and/or a cumbersome experience for the human, this scheme isn't going to work.