A smart, video-camera-equipped, wi-fi connected doorbell sends you an alert you when visitors arrive at your house or packages have been delivered, and you are not there. You can monitor your front porch easily. 

You can use a smart doorbell camera to screen visitors, even when you are inside the house. This is a useful feature for elderly people.  The moment someone pushes the doorbell, the camera is activated and you can who it is.

Some smart doorbell camera models will even record suspicious activity around your door and entryway.

Good smart doorbell cameras are easy to install, record high-quality video, have an easy-to use app, and  provide a quick response time between event (detecting motion or a press of the doorbell button) and notification. 

High end doorbell cameras are even equipped with motion detectors.

The best smart doorbell camera: SkyBell HD (Effective motion detection, high-quality video, full night vision, a live-view feature, easy-to-use app)

The second bess smart doorbell camera: Ring Video Doorbell (works with many kinds of smart hubs)