SCT-220 is kind of wireless magnetic reed switch, and it can be widely installed at door, window, or other open/close applications. It is very compact and light, and very easy for you to deploy a burglar-proof living environment by it. 
Function Specification - ZigBee Pro (2.4GHz) RF interface  - LED indicator  - Up to 1 year battery life - Wall-mount & tamper-proof  - RSSI (Received Signal Strength Indication) supported