Other than coming up with your own solution, similar to what LordHamster describes, PetChatz seems like the closest thing. And rather than mounting on a wall, you could fashion some sort of a stand for it so it sits on a table.

Edit: I'm actually thinking LordHamster's suggestion is your best bet. If you have an old laptop (or desktop with monitor), all you'd really need to do is set up the monitory/display somewhere and hook up a pan/tilt/zoom camera, which seem plentiful and affordable on Amazon. Hook up to an Echo or other bluetooth/wireless speaker with mic for better audio. Enable Auto-Answer via skype (or I hear google hangouts does this too) and you're in business.