A good scale which uses impedance to give a reasonably accurate measure of body fat % is fairly cheap nowadays, fyi. I got mine for about £25 in the UK. It's accurate enough to tell you whether your fat is dropping overall, week after week - just make sure you measure at the same time each day (ideally, just after waking up, before having breakfast).
I used one once, and I was skeptical about its accuracy, since it required gender and activity level as input. I still prefer performance as a metric, because it measures fitness.
