Sending data between Mac app and iPhone companion app

What is the best way to go about sharing data between an app running on mac and iphone connected through USB.

I know of a few products like https://www.duetdisplay.com/ that route your Mac's video output through USB to an app window running on iPad.

I want to do the same but instead route my Mac's audio output to the iPhone speaker output in realtime.

I have asked Swift developers and no luck yet. There is a library called https://libimobiledevice.org/ that communicates with mobile devices. Could this be a possible route? Or is this a job for an Objective C developer? Any info helps.