I’m still trying to figure out how to use Unifi cameras as a baby monitor on my Google Home Hubs, and came across this thread (there’s no audio with the stream component).
One option I found in this thread is the FFmpeg Noise component. It won’t stream to mp3 as far as I know, but you could use the binary sensor to them create a text-to-speech alert on a Sonos or Google Home. In my case, something like “your kid is out of bed” could be useful (and probably creepy) coming out of my bedstand speaker. Just thought it was worth mentioning if it happened to support your use case.