The tool that's being used is Tools -> Inquiry -> Distance (which appears to invoke MEASUREGEOM).

When I use it in ACAD Mac 2015 and 2016 it shows a crosshair with a ? next to it. It does still work though as I can click two points and it will advise the distance between them. Attached are a few screenshots of what mine looks like.

A couple of things I've noticed with how it works

- In Inquiry Result.png, it pops up the result in a little window next to the crosshair. If you have dynamic input disabled, you won't see this. It can be toggled with Command-Shift-D (or the icon in the status bar).

- In Inquiry Result 2.png, it displays the result over several lines. If the history is not showing, you will only see the last line, meaning you can't see multiple results easily. If you click the arrow on the right side of the command line, it will display the history until it is closed (expand this before you measure distances).

EDIT: Hang on, I swear there wasn't this many replies when I was typing this... Kind of makes my post redundant lol