A smart doorbell is an internet-connected doorbell that notifies the smartphone or other electronic device of the home owner when a visitor arrives at the door. It activates when the visitor presses the button of the doorbell, or alternatively, when the doorbell senses a visitor with its built-in motion sensors. The smart doorbell lets the home owner use a smartphone app to watch and talk with the visitor by using the doorbell’s built-in high-definition infrared camera and microphone.Some smart doorbells also allow the user to open the door remotely using a smart lock.