The Mijia Smart Light Sensor is designed to measure ambient light, in order to create scenes and automations based on the available light. You can program an automation, so that when it gets dark, your porch light comes on, or close your smart curtains, for example.
The sensor can measure as much as 83,000 lux or as little as 2 lux. The sensor is ZigBee 3.0 and uses a CR2450 coin battery for power. It can be used outdoor and is waterproof (no details on IP rating yet).
Currently compatible with the new Mi Smart Gateway and the Aqara hub.