Enter: ChiliPad. This is not your daddy's electric blanket!
I found this mentioned on both OhGizmo! and SlashGear. ChiliPad heats or cools water and pumps it around your mattress. This allows you to alter the temperature of your bed to between 68-118°F, in 1°F increments. With this, you can sleep comfortably and ease the strain on your HVAC at the same time, saving you money. Well, saving money after a long break-even period... it retails between $479 and $999, based on size and single/dual-zone.