I second what jeff007 said - just need basic face detection to filter out false alarms. Modern machine learning algorithms like this can easily be compressed to run on-camera.
In addition to the person notification, have an option for a SPECIFIC person notification. This is especially valuable for women who have a restraining order against a violent husband, ex-husband, ex-boyfriend, etc. Such women would want to respond immediately to a notification only if the person with the restraining order shows up (and not the UPS delivery person, e.g.). I imagine this would work by putting a photograph in front of the camera, then pressing a special option such as “train AI to recognize person in photograph.”
I know part of the issue with some companies implementing this is that some states are starting to make facial recognition an illegal thing, Illinois was a big one when it happened there and I have heard of some states following suit