You can get scales that measure your body's electrical resistance to calculate your fat content. I picked one up at Wal-Mart the other day for $40.
It's a good ballpark figure and you can tell if you're improving, but it's not as reliable as a trained person w/ calipers. Diuretics such as caffeine and alcohol can screw up the readings. I have to find those rare moments when I don't have one or the other in my system, and then it does read quite consistently for me.
