prim1. I'm not a commercial pilot and don't pretend to be so, but we were always lead to believe that the primary function of the markers was to give 'distance to go information which would be corellated with the passing height/altitude of descent on the glidepath. Therefore providing exactly the function you describe. Also, more importantly, distance info to check rate of descent on a LLZ only approach. Isn't this one and the same thing?
Spiney.