SMART DOOR SENSOR BroadLink + S3 HUBBroadlink Smart Door Sensor DS4 FC with S3 Keep an eye on the opening and closing of doors in your home from your phone. With the Broadlink DS4 Smart Door Sensor, you can find out if a door or window has been opened while you're away perfect for people who put safety first. You can also program the sensor to come home on your own. When you open the door, you can turn on the lights in the relevant rooms, play music or turn on the heating. Everything