These Hokkairos have been very popular in Japan and all over the world (Lam even had one when he was five—his parents made him sleep on a stainless steel bed), acting as a self-contained hand warmer you stick into your pocket in the winter. As you can see in the cool warm video above, you just need to break the coin-shaped container to cause a chemical reaction. It's "semi-permanent," so you can heat up the thing once it's cooled off (probably not in a microwave) for use again. It's only $4 each, which is definitely a price not too much to pay to keep our fingers intact when high-fiving Eskimos. [Strapya]