Indeed sounds great, maybe we can collaborate a little as I may start down the path on my own.
I agree that with a few known constants and formulas this should be straight forward. I don't see how this would be any less accurate that approximating the quantity of water in two tiny vials, putting 4 approximate drops into those vials and then, more or less, guessing as to which color the vials have turned... Especially since said color varies depending on how much ambient light you have outside. I would think that even if the readings are off from reality by 10-15% they are as good if not better than what Im doing today.
Not looking for a precise quantity of chlorine, not trying to put a rocket on the moon here by mixing hydrogen and oxygen in precise quantities of atoms.... Just trying to keep the pool from turning green too often and keeping it more or less comfortable for swimmers.