[Window & Door Alarm Sensor for Home Security] SwitchBot Contact Sensor can detect the opening/closing of doors and windows, guarding security of the elderly, children, and pets. With the built-in light sensor, it will automatically trigger the Switchbot Bot to turn on the light when someone moves when the environment goes dark. The magnets need to be aligned with the bottom of the body, and the distance between the two components needs to be less than 1.2 inches (30mm). [Detects People Leaving or Entering the Home] With the built-in motion sensor, Contact Sensor will know whether you are leaving or coming home, making it possible to trigger the different actions you set in the "Scene" in the SwitchBot app. When it detects you leaving home, the appliances will automatically turn off, and when it detects you coming home, the appliances will automatically turn on. (SwitchBot Hub Mini required) [Easy to Install & Place It Anywhere] Thanks to the small and wireless design with long battery life, you can install Contact Sensor tool-free and get it set up in seconds. Place it on a medicine box to track whether the elderly are taking their medication, or place it on your pet's cage to know if your kitten has slipped away. [Part of the SwitchBot Ecosystem] Connect Contact Sensor with other SwitchBot products and set up a Scene in the SwitchBot app. When windows are opened, the SwitchBot Bot will be triggered to turn off the Air purifier automatically. (SwitchBot Hub required)[Remote Alert Notification & Voice Alarm from Alexa] You will receive a door-open alert notification on your phone if a suspicious person enters the house while you are away (SwitchBot Hub required). Alexa will start a voice alarm to scare off any burglars, ensuring your apartment security.