I used to have a weak aura that added a purple fog around the screen so i could know better when i was in stealth, anyone know any addon that does the same thing?? or i just have to relearn no know when i’m stealthed? 
Is your stealth/prowl key not greyed out when you are stealthed?
I haven’t experimented, but there is an API function IsStealthed() that indicates whether your character is stealthed. It is supposed to work with Prowl, Camouflage and Shadowmeld as well.
It doesn’t appear to be secret, and even if it were, I think you can set an Alpha (transparency) level on a texture from a secret bool.
An addon could monitor it with the UPDATE_STEALTH event.
So it should be possible to write an addon (or fix the one you were using).