After updating its smoke detector and camera, Nest has finally decided to update the device that made the company famous; its Thermostat. The new smart controller has a slightly thinner profile, larger and higher-resolution display and will now alert users when their furnace is acting wonky. To make figuring out what's going on without walking across the room easier, the third-generation device will now display the target or current temperature or an analog or digital watch face on a larger display that's activated whenever someone walks into the room. The Thermostat now has a 480 x 480 (229 ppi) display. While the display got larger, the profile got smaller. The width of the device is now 1.21 inches instead of 1.26 inches. Not exactly a huge difference, but slimmer is slimmer. For furnace owners, the Furnace Heads-Up feature tracks shutoff patterns to see if there's a potential problem with the heater. This feature will be released for the first- and second-generation Thermostats later this year. The new third-generation Nest Thermostat is available now for $249.