Hot/Cold blanket

I find that, even in the summer, I cannot get to sleep or stay asleep without a blanket on me. However, this can be uncomfortable and cause its own problems when you're already too hot.

I propose a blanket that can be both hot and cold at the same time, since it will usually be your torso that is overly warm, while your limbs are cool, but what do you end up sticking out of the warm cozy blanket? A leg or an arm.

This could be as simple as a blanket with a flap in the middle that can be tossed aside when you're too hot, leaving your torso uncovered, but blanket on your arms and legs. Or as high tech as a blanket with programmable heating/cooling elements, setting the temperatures in different areas of the blanket to suit your needs.