The mydlink DCH-B112 Smart Door/Window Sensor is a discreet contact sensor that detects when a door or window is opened or closed, giving you a trigger for automating your smart home. It works with Amazon Alexa or the Google Assistant for convenient hands-free voice control. Take it to the next level with IFTTT recipes to automate with other Smart Home compatible devices. Save time, and enjoy a safer, more comfortable home. No more wondering if you left your door or windows open. The mydlink Smart Door/Window Sensor lets you check on them from anywhere with your phone. It also sends an alert whenever a door or window is opened, or when someone tampers with the sensor.