SOME Desk Host is installed. It appears in the menu bar when you launch it.

Open the app on your iPad and pick this Mac. You'll be asked to confirm a pairing code once.

To remove everything later: drag SOME Desk Host to the Trash and delete /Library/Audio/Plug-Ins/HAL/SOMEDeskMic.driver, or run the uninstaller in the app's menu, which also restarts Core Audio for you.