I was reading through the Armour History tables and noticed a reference to "improved Mk6 bio-monitors". I'm guessing it's something that got chopped in editing. Any idea what effects these would have?

Well since its standard for power armor in use by astartes to have bio-monitors, I'd guess it would give a bonus (+10 maybe or +1/2 DoS) to any medicae test on the character wearing a suit of power armor with improved bio-monitors.