I received the siren today and made a short test:
It seems to be absolutely perfect for the job:
- Theres a small pouch lithium-ion-cell included that you can see on the photo
- A disconnection from ac is reported within a second
- If you like you can additionally use it to send an accoustic and optical signal
- Here a picture of the opened device
At the moment it’s not directly discovered by zigbee2mqtt but I raised a PR so the current manufacturer code is accepted. I can keep you informed when the PR is accepted if anybody is interested.