Currently a video doorbell can pop up a picture on your phone so you can make the same decision. Most can also act as an intercom.

My first reaction was to like the idea as a nice extension to existing functionality, I don’t see it working.

• Someone you don’t want to see has no reason to be honest: solicitors are already in a gray area trying to trick you out of your money and there’s no reason it would stop here
• Someone you do want to see may be annoyed and discouraged at jumping through too many hoops. You’re not that important to deal with that