Nest Labs, the home hardware maker co-founded by two ex-Apple luminaries, is today unveiling its second product, Nest Protect, a $129 smart device that hopes to do for the smoke and carbon monoxide detection market what Nest’s Learning Thermostat did for home temperature control. That is, it wants to turn what has become for many a mundane, malfunctioning domestic necessity into a reliable and stylish must-have. Artfully designed, connected up with your smartphone, and full of features that work better than what it wants to replace, Nest Protect is the startup’s biggest play yet to make a global name for itself, and position itself as a serious player in the connected home.