Amazon offers the third-generation Nest Learning Thermostat in Stainless Steel for $198 with free shipping. (Home Depot charges the same; B&H Photo Video charges a buck more.) That's the lowest price we could find by $2, although we saw it for $49 less last November. Improving on its predecessor with a slimmer profile and bigger display, this thermostat "learns" how you set your home's temperature, downloads data, and can be controlled from your smartphone via WiFi.