Serene Innovations CentralAlert Door Hanger With Door Knock Sensor,Dimensions: 2.5" x 3.8" x 1",Each,CA-DXHPrice: USD47.95 Serene Innovations CentralAlert Door Hanger With Door Knock Sensor is easy to use, just hang it on your door knob or handle. It is ideal for hotel room or bed room applications. Safe and secure since there is no visible part outside the door. It detects the vibrations from knocks on the door and sends alert to the CentralAlert receiver to notify you when someone is knocking on the door. Ideal for both home and hotel stay applications.Other products from H e a l t h P r o d u c t s F o r Y o u |