It depends on how you look at it. Right now Ring is the primary company in this market, but if they get real traction it would be easy for Google to add a button to a Nestcam and make a Nestbell. There are Chinese companies flooding the security market with low-cost and good quality equipment.

Ring got a $200M valuation. Assuming investors would be happy with a modest 5x valuation, Ring is going to have to sell several million doorbells to make that happen.