Using iPhone7 as a microphone for MacBook
Try this steps:


Download Microphone Live on your iPhone
Put the iPhone in Airplane Mode (not sure why, maybe it works even without this step)
Connect your iPhone to your Mac with a Lightning to USB cable
Open Audio MIDI Setup on macOS
Go to Window and click on Show iOS Device Browser
Click Enable under your iPhone
Open the previously downloaded app on your iPhone
Open Preferences on macOS
Go to Sound then Input and your iPhone should appear in the list
Select your iPhone and you should be good to go!