I have some more documents on the topic (and others), but I will have to translate it to english first.
But you should have a lot to go with, from the already provided explanations .
Here a couple of linkt to another free VU-Meter (don’t know about mac version):
Stereo version:
http://www.vst4free.com/free_vst.php?id=1216
Mono version:
http://www.vst4free.com/free_vst.php?plugin=MonoChannel&id=1215
These also have some interesting features added, but to start out with the default setting first is my advice.
While at it, they have some other tools as well:
http://www.vst4free.com/index.php?dev=Sleepy-Time_DSP
Happy metering.