I like the whole idea a lot.
The only difficulty I see is getting it to be reliable and accurate to a degree. Post up some pics, so we can all get an idea of exactly what you got going on, and maybe we can refine this thing online.
FILSTAR Pimp #2
75 gal heavily planted,50/50 Black beauty,Eco-complete substrate, Pressurised CO2 with solenoid, ph controller, AB Reactor 1000, 330 watts 9325K GE PC lighting,Ehiem Liquidoser, 2-Filstar xp3 canisters.