For $99 at Target we bought a mattress warmer with a timer just as the Bomb Cyclone dropped our temps to 10°F. Most effective $99 I've ever spent -- our Texas house cannot stay above 60°F in that weather.

Someday the same product will be controlled by a Home API and your phone and BTLE and cost $99/year for the app, but for now it has escaped the relentless march of "progress".