Flashes light with knock on the door. As BONUS it can be turned on and used as a flashlight when needed.
Senses door knock vibration
Flash of extra bright light responds for several seconds
Sensitivity switch ensures maximum results
Lifetime LED light never needs replacing
Use at home or away
Simple to install.
Uses 9 volt battery (not included)
Permanently install with a screw, attach to door with velcro or use hanging bracket included.