I am looking for an alarm system that does not require wiring between its different modules, but at the same time I do not want it to be on the internet.
The only two modules I'm looking for are door/window open and motion detector. And a siren of course. The max distance between every two modules is 10m and the max spread of the whole system is 20m. Drywall interior walls.
The system can use a Wi-Fi network that is not connected to the internet.
When triggered, the system should emit an audible siren. The idea is that the alarm would be in use only when people are inside, and if it triggers, the dwellers can call emergency services themselves.