TP-Link Smart Open-Closed Sensor

The CS100 Smart Open-Closed Sensor from TP-Link works in conjunction with the SR20 router (available separately) to alert you whenever a door, window, or drawer is opened or closed. The sensor connects via Zigbee protocol to the SR20 router, which works as a hub. An included AA battery provides up to 2 years of battery life. The free Kasa app for iOS and Android devices offers remote viewing and management of your devices. Additionally, you'll be able to receive notifications from anywhere.