watchOS 9.2 beta seems to have that. All devices need to be running the latest beta for it to work. You need a HomePod or ATV on latest beta to serve are the hub. I don't use "keys" so haven't been able to test that. But I have successfully shared my "Home" with other "residents" (with their device on latest beta) and they can control the HomeKit devices. So I assume when 9.2 is released it will be included.