Kind of depends on how much of a water chemistry geek you are. Some people just use the test strips and people like me are looking for a little more insight.
I have a bromine-sanitized spa (non-chlorine) and I use the Taylor K-2106 FAS-DPD Bromine Complete Test Kit every other day and track my chems on the PoolCloud app. Then I transfer the data to a spreadsheet with graphing to spot trends.
Geek, I tell you, geek!