Yes, I use the cast-web-api. My google home devices announce when the sprinklers are about to start, garage is opening, closing, coo coo clocks, door openings, and tons of other things.
For the cast-web-api to work, a node.js server must be currently running on your home network, 24/7. That’s the only hard part. You can run it on a computer that’s always on, or any device that’s capable. Some use rasp pi devices etc. I run it on a samsung tablet that is my home’s ‘control panel’ for ST. Since it’s always home and always plugged in, it works great, even when the tablet is “asleep.” For android the node.js app I use is called Dory.js.
Most people use webcore to play custom sounds but there are tons of options created by the community.
I use a virtual momentary switch for unsupported devices if I want it to announce it, for instance my ge dishwasher works with iftt but not ST. So on IFTTT when the dishwasher is done it presses the ST virtual momentary button, which using “big talker” community smart app, announces it over the google homes. If you want custom sounds to play instead of TTS (words played on Ghome) they have to be “hosted”. Typically I’ll google sound effects and copy the link on a web page to play the sound I want and paste the link into code in the IDE using the community created speaker companion app. It’s not as complicated as it sounds. I can’t find the community speaker app right now but I can share the code if you want.