Questions about Shelly Plus Smoke Alarm

The same subnet (e.g. 192.168.1.0/24) only plays a role when triggering via broadcast or directly. However, I suspect it is more likely via Shelly Cloud. If the fire detectors are registered in the Shelly app, it is very likely that a signal is sent to all of them via Shelly Cloud, as the app also sounds an alarm. Many households now have mesh or multi-AP solutions.

We purchase the individual product from another supplier at a different price, which has a corresponding effect on the sales price.

The Shelly Plus Smoke smoke detector comes with a battery that has a service life of up to 5 years. So you don't need to buy an additional battery.