More information here: https://nest.com/ca/doorbell/nest-hello/overview/
Nest Hello lets you know who’s there, so you never miss a thing. It replaces your existing wired doorbell and delivers HD video and bright, crisp images, even at night. It’s designed to show you everything at your doorstep – people head to toe or packages on the ground. And with 24/7 streaming, you can check in anytime. Or go back and look at a 3-hour snapshot history to see what happened with Nest Aware.
Working with Nest Hello, a Google Home Mini can announce someone's at the door.