I recently got a Google Home, and I’ve set it up to announce BT events using the MediaRenderer SmartApp and BubbleUPnP server running on my Synology.
This combination strikes me as sub-optimal for a number of reasons, not least of which is the long delay between the time an event is triggered and an announcement is made on the speaker.
I stumbled across a DTH that implements the Cast API here, and I’m working on a Docker image for the node.js proxy that is required. I’d be very interested in seeing Google Cast devices supported as a native device type for BT.