Recs.
Updated
Specs
Pros
Pro Available in either hardwired or battery configurations
While the battery model ($110) is rated at 10 years of battery life, some prefer having the piece of mind knowing their potentially life saving piece of hardware is connected into the power supply of the house. The hardwired version costs $120.
Pro Quick reaction time to smoke and CO
The most important aspect of an emergency sensor like this is that it works quickly, giving you the biggest head start possible so you can get out safely. OneLink is a company that has been working with detectors like this for years, and this is one of the fastest smart thermometers to respond to smoke and CO. However, the same can't be said about the time it takes to send a notification to your phone (which is at least a minute and a half - a very long time considering your house is burning).
Cons
Con Internet connectivity doesn't add much for detectors
Receiving notifications of a fire or high CO content may sound life changing, however it isn't actually all that useful. You'll get notifications - sure, but you can't really act on them (and they'll likely arrive too late anyways). If you're away from your house you should really verify there is an actual fire before calling the fire department. If you're at home, having a notification on your phone isn't going to be any faster than hearing the alarm go off. Internet connectivity doesn't really add much utility right now.
Con Doesn't ring continuously when another detector is set off
While everything works fine when the OneLink Smart alarm detected smoke first, when a dumb detector noticed smoke first the OneLink Smart alarm would ring for a few seconds, then turn off. This is a huge issue, as you want the detectors to keep ringing to make sure everybody in the house wakes up and gets out.