I am the developer of one of the community App/Driver combos using Googles new (last year) API: [Beta] Google SDM API - Nest integration
As mentioned, the setup is a bit complex (can thank Google for that), but I've tried to make the steps as clear as possible in the GitHub README file. Officially, this supports full control of the Nest Thermostat, and monitoring of camera/doorbell devices - motion, person, and sound events, as well as automated image capture when an event occurs. There have been reports in the last couple months that the integration no longer receives events from the Nest Hub Max - though Google claims its camera should report - seems like possibly broken by a firmware update on Google's side.
Hope this helps - take it for a spin if you like,and drop a note on the main thread if you have issues, will do my best to help you out!
