[Jenda_]

And pretty terrible in my experience (tested two, one noname and one branded, unfortunately forgot the manufacturer/model number).

First, there is a fundamental constrain that it measures impedance only through legs and a little bit of belly, but no upper body (at least here in .cz, no consumer-grade scales have hand electrodes). I do road cycling as the only sport, and therefore get extremely skewed results as I have strong legs, but the rest of the body is much weaker.

Second, the measurements are almost non-repeatable. You get tens of percent difference across measurements, god forbid if you suddenly have moist feet etc. However, both scales used firmware cheating to mask this noise: once you set up a "profile", it will remember the initial value, and then change the following measurements only slightly. However, set up a second profile (preferably with a slightly modified age etc. to prevent advanced firmware cheating) and you get completely different results.