Really, I think the way mps does it is the only reliable way to track this kind of progress.

Tanitas don't measure % body fat. Neither does immersion in water, air displacement, callipers, any method. They are PROXY measures - they measure things that are ASSOCIATED with a certain % bodyfat.

The only way to MEASURE % bodyfat is post-mortem dissection - ideally, by rendering the body.

In the absence of this direct measurement method, all other methods may be used with some modicum of accuracy, but because they are estimates based on proxy measures (which themselves are prone to error margins) and statistical models (with their OWN confidence intervals, which are rarely if ever mentioned), I really don't see much point.

The same person using the same measurement tool (i.e. callipers) on the same body part for tracking purposes is very reasonable.

Anything else is so error-prone, I have little faith because of the reliability issues.