Not so hard.
Just a small add on to one of those video camera like devices with a key pad as for a multi unit property or gated mansion. Play a recorded message after the caller presses the ring button. As an example “Welcome, I am very busy today and may not be available. Please do not waste your time - are you a product specialist - please press one, are you interested in religion - please press two, are you in need of financial assistance - please press three, if you would like to know me better - please press four and leave your personal contact details after the beep, if I know you - you will know which button to bring joy, thank you - have a nice day.” Please press # to hear these options again.
It may be best to leave the responses to options 1 thru 4 to each householders personal preferences. You might also like to start the intro with a sort note advising - “for quality and training purposes this visit may be video recorded. If you do not wish to be recorded please …”.
Crowd funding anyone?
You may need to provide your own accessories to suit to help the price down, and limit the developers liability in the instance the doorway has inadvertently connected to an electric cattle fence. Just kidding!