Now that Nest Hello is available and ready for mounting in place of your current doorbell, it makes sense that Google would prepare its Assistant and Home units to work with it. And today, they’ve already done that, by allowing you to pull up doorbell feeds with a simple voice command, as well as hear notifications when someone shows up at your door.

Source: Google Adds Doorbell Support to Google Home for Video Streams, Notifications When Someone Rings It | Droid Life