Yeah yeah...I know what some of you are thinking...I want to use this as a spy cam for something else. 
I've got an old iPad Air 2 and iPhone XS I could potentially use. I see there are a few apps in the App Store that can supposedly do this, but none really seem to be all that popular. I suppose I should just pick one and try it out, but wanted to see if anyone has any suggestions. It'd be great if I could get notifications if he's barking, but not a dealbreaker. (I've figured out how to do this with a personal automation now that iOS 15 has a trigger for sound recognition.)
Basically just looking to do a home-built Furbo without all the fancy frills... I get a notification that he's barking, then I can view the camera to see if he's barking constantly, single barks, or false alarm.
I'd be open to other alternatives. Are there any cheap HomeKit cameras that would work as well (paired with the personal automation for the notification), or would that be overkill?