Ring's Video Doorbell is held in place by two tiny torx screws from below, and they offer a theft guarantee. Somebody steals it, they replace it. The Ring mounts to a backplate that you then screw into your wall. In my case, my attempts to drill into my stucco failed (even though I had a proper masonry bit), so I gave up and used Gorilla Glue to attach the backplate. The only way it's coming off is with a chisel or some kind of really interesting solvent.

A couple other things about the Nest Doorbell: Nest has some kind of "Nest sense" thing for its cameras that can distinguish between different faces. You can imagine this being an intriguing part of an integrated security system if you had all the other camera goodies that Apple is doing with the iPhone X. Also, they've hacked up a "warm welcome" feature where the motion sensor trips and the lights glow. "Hi, we're here watching you."