I was in a local sporting goods store this weekend and saw a scale that not only gave your body weight but also your body fat percentage. Almost bought it for $40. The reason I did not was I could not find the magin for error posted anywhere on the box. Also in small print it said that this scale should not be used by athletes. Athletes was described as any ony with a resting heart rate of less than 60bpm. Or some one engaged in riroros activity 2 or more times a week. It said that this scale was programed for the sedintery person and that ther was another model designed to be used by athletes. This store did not cayyr that model. Has anyone used these types of scales and how do they work? How accurate?