Sonoff SNZB-04P Zigbee Door/Window Sensor is a low-energy wireless device that informs you about the opening/closing status of a door or window by detecting the separation of the magnet from the transmitter part of the device. It can be connected to the Bridge (not included in the package) and used to create smart scenes to trigger actions based on the door/window status. The device features low energy consumption, a low battery notification, and an easy installation process.