I think that a system like this, would cost in the thousands. Which would mean that the thing will control things like PH, KH, GH, Water changes.... the list goes on and on.
Here is my input. Which, is based on truth. If you spent $2K on a maintance system for your fish, you probably have at least that amount in fish alone. What are you gonna do when say, 2 years down the road, your PH monitor goes off the deep end, and you end up with an acid bath of a fish tank? A water level sensor fails, while your on vacation, or at work, and is now pumping water right out of the tank? I know that you can have fail-safes, but even they fail. I know that sensors and such fail, because I deal with them at work, in a factory, where they are used excessivly, and fail even more so. I run a $500K robot welder, and guess what? It began welding in the wrong spots, for no apparent reason. It is 5 years old, but how many of us are using heaters, filters, and tanks that are over twice that age?
Sorry for the ranting. My basic thing is, sure build it. When you have it working that your "machine" hasn't killed any fish, flooded your floors, messed up water changes, screwed up water parms., forgot to add dechlonrinator, or any other detrimental thing to the tank, for like 10 years, let me know. I might look at it then. Sure, I can do all those things myself, but they are my fish, and I take care of them. I don't have a robot follow my dog around scooping his poop up, do I?