Their main page says:
Almost all of them still go unmeasured! Four out of three thousand is about 0.0013%.
Track your Ketone levels
Optimize your Vitamin C levels
Regulate your Bio-Acidity levels
Follow your HydroStatus
Maybe they should charge 0.0013% of their current USD379.95? About USD0.005.
Ketone, vitamin C, pH, specific gravity and several other factors can all be indicated by a simple dipstick which costs pennies. And it is accurate enough to point out where you need to look further - even if numerically rather approximate.
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There is always the problem that these things can show short-term variations which are of little or no significance. If your test time, using the device or a dipstick, clashes with a high or low value of an item, you might be somewhat misled. However, if the test is inexpensive enough, you can perform several tests in a short time and see how consistent your results are.