How about a gadget that knows you better than you do? The Nest is a smart thermostat that learns home heating and cooling preferences and handily programs itself.
Now in its second generation, it comes with an array of energy saving settings and can be controlled remotely through Nest's website or your smartphone -- making it the ultimate gift for the energy efficiency geek.
Plus, the Nest thermostat was created by the developers of the iPod, so it also has that sleek, minimalist design that makes it more than just thermostat, but drool-worthy gadget too. (Nest Learning Thermostat, $250)