If you enjoy cold weather camping and want a good nights sleep, check this out. It's the military's modular sleep system, or what I think of as a fancy sleeping bag.
Trust me when I say, it's warm. Many of my friends, like Duke, own and use them. I climb into mine nude (really) and within seconds you're warm and snug as a bug.
This site offers the bag for about a hundred dollars, cheap. Many sell upwards of twice this price.
It's a good 'thing.'