Hive Window or Door Sensor.Brand New and sealed. 8 available. I bought these a while ago as I was going to set up a home security system, however never got round to doing it. Hive are now discontinuing their home security, however these sensors are still usable in line with other Hive items - such as being able to connect them to your Hive Thermostat to turn off the heating when opening a window, or switch off the lights when you leave the house.
eBay