An add-on that makes visible a visual flight path in landing even to a non ILS airport? First time I hear it.

A link to this add-on would be appreciated.
Anyway at 27 nm out generally you can begin to receive only the LOC signal, while the GLIDE comes alive around 20 (I'm going by memory) depending mainly to the steepness of the glide-path (in FS, real world has other variables attached to it). The signal on the HUD in real world is dependent by the airport having a ILS, if the airport has no ILS, the HUD will remain blank. At the same time the signal on the HUD will be as much accurate as the ILS is. Meaning no CAT III landing on a CAT I ILS anyway.