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

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.