Originally Posted by AUFishman
You can get electronic readers, but they are not cheap. When I was in grad school we had a really nice YSI that took temp, salinity, DO, and pH, stored the data, and uploaded it onto an excel spreadsheet. They cost about $1200, and are a pain in the ass to calibrate. You can get some simpler electronic hand held meters for pH and salinity that are under $100, but again you have to calibrate them regularly. For NH3, NO2, NO3, you are basically looking at the "match the color" deal. None of them are real precise, but two of the more reputable companies are Hach and LaMotte. To get a complete kit you are gonna drop about $200
One thing to add.....
Salifiert makes test kits that are color changers rather than matchers, but they are only for Alkalinity, Calcium and Magnesium (maybe more, but those are the ones I use). I have not found a test kit for NH3, NO2, NO3 that aren't match the color. Nor have I seen any digital tester for those 3 either.
First person to invent one that is accurate and not extremly expensive will be a millionare in a year!
Good Luck