Wondering why it's so special? For one, instead of a maddening periodic chirp to announce it needs new batteries, the $129 unit will simply send a message to your phone. And any time it senses smoke (while you're cooking, a smoldering candle, etc.), a soothing woman's voice announces as much before initiating a loud siren alarm, giving you a chance to proactively disarm by simply waving your hand in front of its motion sensor. Plus, if you already have a Nest Thermostat installed, they can be synced for added security — sending a signal to your furnace to shut down whenever an elevated CO level is detected. There's even a built-in LED you can set to glow brighter in the dark when you walk by to prevent egregious toe-stubbing during late-night trips to the bathroom.