There was an article about high-tech scales in the this mornings paper that caught my eye. BIA is used to measure body-fat and is similar to ICG. There's a good explanation of how these devices work here.
One of the critical factors for these measurements is the number of electrodes (2 or 4) and their placement. The impedance model used for the parameter calculations (TBW, FFM, etc.) is highly dependent on the electrode configuration. Reliability and reproducibility have improved over the years which has made these types of devices commercially viable in the consumer market.
There is also active research in multi-frequency BIA (MF-BIA) in order to "accurately monitor acute and chronic changes in hydration during various diseases and their clinical management" (see ref). A commercial MF-BIA product is available from Xitron that uses Bioimpedance Spectroscopy (BIS) for estimating intra and extracellular water (ICW and ECW). These measures can be particularly useful during dialysis treatment.
