I think my system is pretty innovative:
A pin-hole camera looks out through a window pane on the porch. The doorbell is connected [through a relay] to a security DVR which takes a snapshot of whoever is at the door at that instant and emails me a photo of the visitor.
I'll add an intercom someday...
Last winter, a company tried to deliver an appliance when I was out of town

, I got the email, saw who it was and I called them and rescheduled for the following week.
I can't attach the sample photo here for some reason..
