I'll look into the Sonos API. The problem I've found with other casting/streaming APIs (Google Cast in particular) is that it expects a single URL to stream from, whereas Ambiphone is just loading individual sound files and playing them simultaneously on your device. It should work fine over Bluetooth but I appreciate that's not the best experience with Sonos and other smart speakers
It's not out of the question at all, I just need to figure out how to combine the sounds server-side and stream them out. On the plus side it should then be pretty simple to make work across different smart speakers, I'm just not sure how complex/expensive it would be to get set up
