Water displacement is the gold standard...all other methods are only as good as the equipment and/or the operator. (IMHO)

OK, that being said, I use TANITA body fat scales. HOWEVER, I don't worry about if they are absolute, I only use them for trend. I've never had a problem getting a reading but there are several factors affecting bio-electic. Hydration levels, body energy levels (like the higher electrical output after exercise, and even if you do a measurement after lying down are a few factors to consider. I use my scale twice a day, first thing in the morning and last thing before bed. I average these reading across a 7 day period to minimize daily "changes".

YMMV.