With Continuity Camera, you can use your iPhone as your Mac webcam or microphone.
Watch on a Mac - Apple Support
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Messages User Guide for Mac - Apple Support
Use Cinematic mode - Apple Support (IN)
Belkin's iPhone-as-a-Mac-webcam accessory is now available
How to use your iPhone as a webcam for Mac with Continuity Camera
Apple's Continuity Camera lets you use your iPhone as a webcam
Use Universal Clipboard to copy and paste between your Apple
This tiny Belkin accessory allows iPhone to be used as webcam for
Use Your IPhone As A Webcam On Mac Apple Support, 54% OFF