I have a Tanika Digital scale which has the wonderful extra feature of a body fat calculator . It does this by sending a small current from one heel to the other, since fat has a different resistance than lean body mass it can estimate body fat%. I have found it quite accurate if averaged over a few days. Just like weight it can give you some oddball readings now and then. Hydration level etc causes significant swings in %. I track readings daily calcualting lean body mass. It is odd watching the correlation between weight and fat %. Overall it is a useful tool as long as you realize it has its variances.