Application highlighter.. or something?

Hi all,

I could have sworn that I saw something like this somewhere but who knows..
I am looking for something that will dim, fade or black out the part of the screen that I dont want to look at/am not using, sort of like how it does it in expose. Like I have a few apps running and I can click on one thing and I will only see it highlighted and everything else blacked out, or if Im watching a lower res vid and dont want to watch it full screen and the screen will dim outside the running vid(quicktime app)
Does anyone know something like that.

Thanks in advance,
Meghan

F10 on mine will black out everything except the currently active window.

Don't really know what that feature is called and don't believe I've ever used it for anything either.

Think

Enjoy