I think that any method at the extremes, particularly in the overweight category, is bound to be problematic. I use near-infra red technology to determine body composition, and that also has issues at the far end. I do not like to use calipers because they are very intrusive to me.
Personally, I often do not determine body composition at all when I deal with a very overweight client, unless I feel that this person is truly comfortable with it. I feel it’s just piling on the bad news.
What I began to use is the concept of the waist-to-height ratio rather than BMI. This one is a simple calculation, easily repeatable by a client, which tends to identify those who have ideal weight but high body fat percentage.
Having said that, it’s great to have a quick tool for determining body fat, and I have heard good things about Tanita scales.