While the Nest Protect Smoke + CO2 alarm is great for those who want a 2-in-1 device that connects to several smart home devices, there’s something to be said for the Roost Smart Battery. This $35 gadget plugs into any existing smoke or CO2 detector and makes it a smart device. Now, when your alarm goes of, it will alert you (and others) on your smartphone, from where you can either call 911, or silence the alarm, in case a piece of burnt toast is to blame.

[Source:- Tomsguide]