SONOFF
Works locallyZigbee sensors: SNZB-04P door and window, SNZB-03P motion, SNZB-05P water leak, SNZB-02P temperature and humidity. Not their Wi-Fi range.
The SNZB-04P has a switch under its cover: prise it off the frame and the hub knows, and the app says "Not clipped in" until it is back. Each one runs on a coin cell, with its battery level on screen.
SONOFF's Wi-Fi devices work through their maker's cloud, so we fit the Zigbee ones.