Wind-up Boots

Apart from the hand-crank, which folds away discretely around the heel when not in use, these look like your standard issue winter boots.

When you're trudging through snow, often your toes are the first to feel frostbite, while the rest of your body is in comparatively working order. But if you find yourself in a freezing tundra while wearing Wind-up Boots you needn't worry. The crank powers a small heating coil in the boot, so all you have to do is kick out the handle and wind a few times to take the edge off the cold and potentially save your toes.

Once you have recovered sufficiently, Wind-up Boots will even help you build a fire. A ring-pull specially designed for gloved hands exposes a tiny nichrome wire and switches the current to dump all of your winding into it, bringing it to a yellow glow, and hopefully causing your kindling to catch.