Bodybuilding.com has the "Fat Track II Digital Body Fat Caliper".
I can't say whether it's 100% accurate, but it's accurate OVER TIME (consistent). It gives a little beep when the correct pressure is applied so that you'll get a consistent measurement every time, which is all you really need to track changes in your body fat.
I think it goes for around $29.99. Comes with a free "Myotape" which is a nice device to measure your bodyparts ($5 value).
There is another one on the market which is more expensive, I think it has "gold" in the name. That one, I think, is made by the same company that makes the Accu-Measure.
Hope this helps.