Detects in real time if a window or door is open. Simply peel off the film and stick it anywhere Sounds an alarm and sends a notification to your phone via the app Two-year battery life Aqara Hub is required to enable this product to work with HomeKit technology. A smart sensor for every door and window. Get extra peace of mind by installing the Aqara Door and Window Sensor in your home - so you always know whether a door or window is open. Turn the lights on automatically when you open the door. When you open the door in the evening, the Aqara Door and Window Sensor send a signal to the Aqara wall switch to turn on the lights. No matter how late you come home, the lights will turn on automatically. Advanced technology. The Aqara Door and Window Sensor detects the current status of doors or windows via the distance of the magnets inside the sensors between the sensor and the magnet. The sensor is also energy efficient and one battery can last over 2 years under normal usage.