Not Only Does This Device Let You Know When Your Door Has Been Opened Or Closed, You Can Also Verify, Using The Apps, That You In Fact Did Not Forget To Close The Front Door. We All Have Those, "Did I Close My Door", Days! This Device Can Also Be Installed In A Variety Of Locations Such As Windows, Cabinets And What Ever Comes To Mind. As Long As Its Within Your WiFi Range, The Smart Sensor Can Be Installed On Anything You Want To Keep An Eye On!