Body Fat Calculators

MFPfriend

So, my gym has a body-fat-calculating machine thing. We enter our height, weight, age, fitness level (average or athletic), and gender. Then we place our hands around the handholds, and then, 10 seconds later, we have a reading for body fat.

My question is: How accurate is this thing? I am down 1.5 percent from a month ago, but I want to know if it's correct.

What's your knowledge on this subject?