altimeter gauge...

i have been trying to find info on how create an altimeter gauge for my flight sim. Can anyone steer me in the right direction? thanks!

Depends on the level of realism in your sim. A real altimeter is just a barometer, calibrated to some pressure level datum given some assumptions (otherwise known as International Standard Atmosphere, or ISA conditions). The change in air pressure results in some interesting calculations to alter indicated altitude.

Of course if you are talking about a standard combat flying game, you're basically going to just be displaying the plane's global y coordinate (assuming y=0 to be sea level). Methods of doing this vary. Outputting the number to screen, the simplest of all, is easy. Add this script to the object:

function OnGUI() {
  GUI.Label(Rect(10,10,200,20), "Altitude: "+transform.position.y);

That's the value you want, but I'd imagine you want to pretty it up. I'm guessing you're intending to go for the classic circular dial, which involves simply converting a numerical value to a radial one. Check out this thread on making a speedometer, the principle is essentially the same: