At first blush, this is a device that should not have to exist. The alarms should have their own built in notifications.

But in real life, almost nobody is going to replace everything in their house with connected versions overnight. So this fills a gap in the meantime.

I just hope the team is thinking beyond just smoke and CO2 detectors... there's a LOT more potential here.

And I wish they would have the notification go to a webhook instead of (or in addition to) the mobile device. I'd like to control what happens with notifications myself, thank you.

Agreed. My first reaction to seeing this site was, "why on earth would I want this over something like Nest Protect?".

Then I realized it's a stopgap provision for people who don't want to replace all their smoke detectors with new devices.

An optional webhook is a great idea. All notification mechanisms should support it.