From my understanding, there are 2 types of horses available now. 1) proprietary cams that work well but being proprietary require a separate app to use, and 2) onvif compatible cams with audio out that sucks.
Seems most if not all cam manufacturers are struggling with delivering onvif 'talk to' capability. I figure (and hope) that there are makers all over developing such a solution. I'd be first in line for a $50 onvif poe amp+speaker!
Kev