Well it "seems simple" in terms of the value you get: your speedometer is only a quick glance down, so until you get used to driving with a HUD, you don't reall

Well it "seems simple" in terms of the value you get: your speedometer is only a quick glance down, so until you get used to driving with a HUD, you don't really appreciate its value. Eliminating all those glances down to the dash really does make a difference! (As for implementation, that's absolutely not a simple problem.)