This does look interesting but Alkalinity is the one thing I always check just because doing the test kit is so quick and easy. It's a hard one to screw up, and unlike phosphate you aren't guessing at a colour. When it turns you have your number. For the record I use salifert test kits.

PH and DKH are cheap in ELOS, not for the rest... $30-40 for all others (Mg, Ca, etc)

Sorry, ALK is $18, but still much cheaper than using electronic device with solutions.