It's a no-win situation. Farmers want their diesel tractors to maximize fuel consumption, without regard to temperature, humidity, altitude, engine rpm or work load. This is going to require sensors and computers.

There SHOULD BE an OBDII type scanner, that tractors would use, that's standardized across brands, makes and models - so driving to a dealership with this tool isn't required.

But, given the population of tractors (compared to cars/trucks) - I honestly don't see this happening. Hell, I think most farmers would be happy with a RESET button that sets the tractor back to factory settings, and makes the computer re-optimize the system from scratch.