The SkylinkNet WD-MT wireless connected home door/window sensor is an add-on accessory for your existing SkylinkNet connected home alarm system Get instant alerts to your smartphone when a door or window is opened or closed This sensor is wireless and battery-powered with low battery detection Compact design and easy to install with included double-sided tape Ideal for windows and entryway doors, and internal doors that might require protection including cabinets or safes