A key new feature of macOS Monterey is the ability to AirPlay content to a supported Mac from other Apple devices, such as an iPhone or iPad, and we’ve confirmed with Apple that this will include Apple Fitness+ workout videos with one limitation.
After starting an Apple Fitness+ workout on an iPhone or iPad, users will be able to wirelessly stream the audio and video to a supported Mac using AirPlay, providing a convenient way to view the workouts on a larger screen. The only drawback to using Apple Fitness+ with AirPlay is that on-screen metrics such as heart rate and calories burned are not displayed on the Mac, but they can still be viewed on an Apple Watch.
Read more at MacRumors.com