I found a meter set that works in SoundTrack Pro for $79. It's really made for ProTools; but the AU side works.
Vsonic Vmeters
It is supposed to work in FCP as well, but doesn't as yet. I've written to them and let them know—we'll see.
Not all the features work, like the log, and if you apply the meter to a track—it fails; but it is a good solution for measuring the levels to the broadcast standard, and a good alternative to the $800 Dolby software stand-alone.
You can download a fully functional version and try it out for 7 days.
Hope this helps.