I used to have a little roll of pH paper, but this was back when I was doing re-mineralization, with kelp and blackstrap molasses etc. and before I ever got into water fasting. I don't think you need it. You go into ketosis as a matter of course, generally three days in, and then you're in it until you're out. :-)
I wrote more extensively on the kit idea, in the other post.
thinking about it now, I'd print out Purinton's fasting manual, (for recreational reading) and some other stuff from Soil and Health library, and save myself having to read it online. I'd also really like (big wish list wish) a rose garden, and some night-blooming flowers outside my window.
sweetgrass, lavender. . . good things to smell. That gets tough, on a wfast. I'd put some beeswax candles on that kit list too. For purifying the air,(no other candles do what beeswax does, I don't know if people are aware of this), and to keep one going, when those moments come that you feel just 'deprived'.(this is just idyllic, of course)