Hey Wilderbud, have a look at Arduino and also Mbed micros. They are pretty cheap, there is HEAPS of open source software out there, which can be easily modified to suit different purposes. You get get different "shields" for arduino which are essentially plug in breakout boards to suit different purposes. Also for sensors, why not just hack an old pH meter, and a EC meter and make it them inputs....would be a shitload cheaper than industrial sensors, depends how big your growroom is tho. Also consider using a mux (multiplexer) to expand your number of inputs. I too have been considering this as a project, just gotta complete, my other micro projects first!