The ChiliBed mattress will not only heat your bed, it will also cool your bed in the summer. It has some coils in it that will carry cooled or heated water. The temperatures range from 48 to 118°F. This technology was developed by Todd Youngblood for Chili Technology and they've already made available their ChiliPad.
It works on technology which is similar to the one that cools computers. This system can also save you money in the long run, as you're simply paying to heat water, not a whole room. It goes without saying that it's a lot cheaper to heat a bit of water that is recirculated through some coils than an entire room.
This kind of hearkens to what a hot water bottle did before, or those heated pads that were inserted underneath mattresses a long time ago. The mattress is also environmentally friendly, since it's made from 100% soy. For now, there is no word on pricing, but they will cost more than the ChiliPad, which retails from $399 to $649.