Yes "always on top" because otherwise we could use the 2496 meters but, as I am sure you know they disappear as soon as you start a DAW or indeed do much of anything else!
You know, maybe we should have a thread on useful Mac utilities, because there are a few I can't live without, and I think many people are blind to how cool some of them are for day to day use. The best of these I get more excited about than major features in big applications, because they affect *everything* I do day to day.
One of them in WindowShadeX, the prime feature is to let you collapse windows to just their title bar - and the second is to make any window on the fly be able to float on top. So *any* window of any app I want to float on top, a quick double press of the control key and that window stays on top.
Failing that, you could always get a second (or third!) monitor and stick the metering app on that - even adjusting the screen res to make it fill the screen if you wish.