I picked up a kit at one point a few years ago. It also came with some other chemicals to test for other aspects of the soil but I never used them. For me, I wanted to know what the natural pH was in order to grow suitable plants but I also wanted to be able to adjust the pH to encourage a few other things to grow better.
There are a variety of soil conditioners on the market and if your soil is too acidic, you can correct it before planting and grow what you want. These conditioners work well with annuals as you can reapply the conditioner at the beginning of each growing season as needed.