I guess when there is bulk energy involved they are called thermo-piles.
Here are the applications I had in mind:
I can use it to cool electronics which is what it was designed for.
You can make a beer cooler.
They may be able to harvest some heat from your hands and possibly power one of my fake perpetual motion machines.
Emily was looking at citizen electricity. I wanted to see what could be done using olive oil and a wick.
So I picked up a couple yesterday to have them around the lab.