Is there any way to control Mac volume from Apple Watch? Is there a way to control a Mac's audio volume from Apple Watch? Apple didn't provide Watch functionality for system-wide Mac volume adjusting as far as I know.
NB: The only so-so way I've found is if audio is playing from Mac iTunes, and the iPhone/Watch is paired with that library via Home Sharing. The volume can then be changed with the Watch Remote app – but that doesn't trigger system-wide volume. It only changes iTunes' in-app volume.
Is there some third-party software for iOS/WatchOS that can accomplish this?
Note about iPhones: I know that the iOS app BTT Remote can control a Mac's volume, but unfortunately there is no Watch app for it.
I've used MacID with great success on my Pebble smartwatch but they also have support for Apple Watch. It's $4 but TOTALLY worth it!

https://macid.co/

The watch app requires the companion iPhone app to sync with the desktop app and control the volume and track selection. 

And that's not all, the iPhone to Mac has a proximity sensor so you can set your computer to unlock AS YOU APPROACH IT and lock if you get up to walk away. 

I hope this answer helps :)