I think you are referring to the heads up display (HUD). This is a new item introduced on the E60 and was not available on the E39.
I have an Origin (OB2) GPS unit installed next to my speedo and I use that as my primary speedometer. It is right next to my line of sight and almost as good as HUD.
M5Board is the best forum community for information on the BMW M5 E60 (V-10), E39 (V-8), E34 (straight 6), E28, F90 and F10. Discuss performance, specs, reviews and more!