Smoke detectors are not only ugly but annoying as well. They only seem to go off when it’s not necessary and replacing batteries can be a pain. According to Nest, 73 percent of smoke detectors don’t go off during a house fire because of died batteries or they’ve been disconnected due to annoyance. The Nest Protect alarm however, can be turned off by waving at it. (hands-free mute button for false alarms) It knows the difference between a real fire and smoke from burning toast. Battery status is reported daily to the Nest mobile app. If Nest Protect’s carbon monoxide alarm goes off, your Nest Thermostat automatically turns off your gas furnace, a possible source of carbon monoxide leaks.