One of the few surprises of yesterday's Made by Google event was the announcement of overhauled Nest Aware subscriptions, slated for early 2020. They'll include all Nest devices you own and utilize Nest speakers and displays as ears listening for smoke or CO alarms. All new plans will also have emergency calling, which allows you to dial 911 right from your smart home devices or route a call away from home to your residence's local emergency dispatcher.
When you're home and can't reach your phone, you can just tell any of your speakers or displays covered by Nest Aware to "call 911." It's currently unclear if you'll be able to use Home Minis or if you'll need to upgrade in order for this to work.
When you're away and your Nest Cam or device with sound detection enabled notices that something is wrong, you'll get a notification as usually. Additionally, you'll see an option to call 911 right from the new feed in your Google Home app. This will route you to a call center close to your home, so emergency responders can be dispatched to your residence easily.
For now, all emergency calling features are exclusive to the US and the new Nest Aware plan, 1st gen subscribers won't get it. It also seems like 911 calling won't come to regular Google smart home device users without a Nest plan. This might be related to address verification tied with billing so you can't use someone else's address and swat them, though Google of all companies should have other means of authentication.