Perhaps to check the magic you can have the wizards use watches? Like... Imagine an older wizard, like a Dumbledore, or Blackstaff pulling out an antique pocket watch and checking their magic gauges. It's a pretty cool imagine in my mind, it would serve to infuriate their enemies due the gesture being rather nonchalant. The measure for the magic will be shown just like a clock face mixed with a pie chart, if that makes any sense, with each 'second' counting for one magic point for beginning mages. As the wizards grow in power, their watches will automatically update to use new units/intervals, like say B-Staff would have his intervals of 100, so 12 to 5 would count as 500 magic points. Some watches have a little window on the clock face that show the date and such, on the magic watch these can tell the exact number of points remaining over the total like a fraction. The watch can glow (to show the general percentage left) but only when the owner focuses on it, to keep the light from hindering their stealth efforts (if there are any). Of course, it can simply be a wristwatch, if that's what the wizard prefers - imagine some rich wizard with his being in the form of a Rolex, hah.

 This can also lead to some jokes on how the watches are useful for keeping a wizard from accidentally killing himself, but can never tell time. Though, I suppose you can keep the hands on to tell time, while using the 'glow' to tell the percentage, and rely on the numbers in the fraction for specifics. I don't think this concept has been done before, but if so... Tell me where?  I never heard of it before, but hey... There's 6 billion+ humans in the world..

 As for a measure for the magic, how about something like 'ticks' if you're gonna work the watch angle? If not, MUM, Magic Units (per) Mage sounds kinda funny. If you want latin, Magus refero, Mage/Magic echos (not sure if it's accurate). I'm not too great with names, heh.. I'm more of an idea sort of guy.