The bioelectric impedence machines have great test-retest consistency, however they won't be as accurate as a water-displacement tests (the most accurate measure) and tend to read lower. Body fat calipers are only as good as the person administering the test, but can be quite accurate. The advantage to body calipers is you get raw data from 6 different sites, which you can refer back to at a later date and see where your body tends to lose fat first.