I agree, once a tank is up and running well monitoring is a mute point.
I enjoy the hydraulic engineering and experimentation side of the hobby. What do the water parameters look like charted when a tank is in its initial cycle? Is a sump a better filter than a canister? Do plants really reduce Nitrates? To what degree? How long can I go between water changes? What effect does cleaning the filter have on the water parameters? Are there mini mini-cycles after a filter cleaning? How much filtering is enough filtering and how much is over filtering? If I turn off one of my filters how will it change the water conditions? If I add a new fish or two how does it affect the balance of the tank? How do the water parameters today compare with the water parameters a year from now?
Are any of these questions significant? Probably not but I would really enjoy finding out for sure. Will it make my fish any prettier?... probably not but I will enjoy finding the answers. For most people it would probably be a waste of money but for me it would be worth in the hundred or so dollar range to be able to find out.
Currently, there is no such thing as a good monitor in the hundred or so dollar range. In any case, with all of these filter questions - redundancy is a nice thing to have

.
I think embracing new technology is in the spirit of MFK personally...
I think most people don't like blowing $300+ on something they have no (real) use for, or when they do, they do it on something with potential use, like an extra filter. But than again, I also believe "the spirit of MFK" doesn't involve grammar nazis. Liking gadgets is not the same as "embracing new technology". And last I checked, MFK is yet to implement an agreement where everybody states that they are going to follow a unified spirit direction. That being said, I believe anybody with the money to spend is free to satisfy their inner gadget fan. I must say the gadget aspect is the only reason why I am attracted to these "solutions".
To the guy that said that you'd have to test each tank after testing a shared sump. A shared sump connects all of the tanks, if one has a water quality problem, it's not just the one tank, it's the whole system.
Of course these things are made for the reef crowds. The cost difference between a reef tank and a fish only freshwater tank is so enormous that while a controller might cost a lot in comparison to most fw tanks, it is a small cost to pay for the security it provides in a reef tank, where there are many many more variables.
From what I know, hanna drop checkers are the quickest and most reliable way to test for things like ammonia, nitrite and nitrate (it's what the salty folk use

). They are a bit pricey (compared to strips), and I'm not completely sure as to which ones are available...