To understand why Tony Fadell is building the world’s most high-tech thermostat with a team that includes several former iPod and iPhone engineers and an artificial intelligence researcher who’s won a MacArthur Genius Grant award, you have to imagine that you’re him: flush with cash after nine years leading mobile devices at Apple, and wandering the world with your family. You’ve just spent six months in Paris on a whim. You’re building an ultra-green home in Lake Tahoe, with a $15,000 heating and cooling system. When your architect shows you the archaic $350 thermostats that control the system, you’re not only genuinely offended by their lack of innovation, but you have the ability, time, and means to make your own.