Today Nest announced its new product, the Nest Protect. It is a combination smoke alarm and carbon monoxide alarm that received the same love and attention the Nest thermostat did. It has an app and connects to your WiFi. It gives you a warning before it goes off and if it a false alarm (I burn toast, often), you can waive your hand in front of it and it will go off.
I think the tricky part is the price. All of the smoke detectors in my house combined didn't cost the $130 price tag of one Nest Protect. I suspect the people at Nest aren't aiming for Home Depot bargain hunters here and I suspect they'll do just fine with this new product.
Have you noticed the way all of these connected devices are slowly pulling us into the smart-house of the future? I'm loving it.