From Doorbird's home page:
You can see your visitors, talk to them and open the door - from anywhere in the world - via smartphone and tablet.
Doorbird can be used with wifi or hard-wired. It has a couple of dry contacts that can be used to ring an actual doorbell locally. And it was pretty amusing to see a still of two LAPD cops taken at 3:45 AM at the front door of a musician client....
