Drawing a 2D Hud on a 3D OpenGL ES scene is a common task when developing games.
To do this without any distortion in OpenGL ES you need to draw your HUD through a matrix different from the projection matrix used for 3D objects.
In the tutorial Jeff takes you through the process of adding a simple HUD to a 3D Scene.
Be sure to check out the iPhone OpenGL ES resources list for more OpenGL ES resources.
source Jeff LaMarche’s Blog