My scale has hand sensors and foot pad sensors. How it can measure skeletal muscle and visceral fat mystifies me.
About 8 years ago, I experimented with a trainer to see if one would teach me anything new, and he showed up on the first day with a floor scale and took my measurements. I count myself as an analytical person, and looked at that methodology through squinted eyes.
About 3 years ago, I joined a gym and the trainer attached several pad sensors to my body and made my lay on the floor for I think 10 minutes. She gave me my BMI, body fat, etc numbers. I don't know what that method is called.
I wavered buying callipers because they looked far too simple to be accurate. I might give one a try for comparison.
I agree the better evaluation is by a credible lab with proven peer reviewed methodologies. Peer reviewed is a term not used a lot in the fitness industry, and rarely used in the powder and pills industry, but that's a different issue.