Instruments for measuring body fat percentage

Okay....so I want to buy an instrument for measuring body fat percentage as that can give me some accurate reading on whether I'm making my weekly progress. Can you guys please help me with what to buy...the pros and cons of each?

I know there are :

1) scales that measure body fat,

2) and then some hand held object, where you hold the thing with your hand

3) some sthoscope like thing that one pushes through around the arm

which is good/accurate..etc?

Please help and many thanks!

I just did a whole bunch of poking around on this (unfortunately, consumer reports hasn't rated these devices). 

My take:

1)  Calipers - hard to use - varied accuracy unless you have help and get the exact right spots each time

2)  Handheld - I've seen one by Omron, none others.  I couldn't find alot of info on this as to accuracy.

3)  Scales - a) one that you just stand on and b) one that you stand on and also has a handheld device - really a combination of 2 and 3(a).  The scale with the handheld together claims higher accuracy based on the fact that it is taking measurements from 4 places (i.e. 2 feet and 2 hands) simultaneously.

I've also seen that it's important to have an 'athlete' setting(s) available to get good readings if you're more lean.

This is one article that may help you get started: http://walking.about.com/od/prbodyfat/bb/body fatmonitor.htm

For the record, I just bought a mid-range one using some credit card points.  They didn't have what I wanted so I just got a basic scale with the body fat/athlete features.  I am looking for directional information to see if my fuel/workout routines are changing my ratios (besides visual confirmation).

Brands that seem to have good reputations and also comments from users at sites like Amazon are:  Tanita, Homedics, Omron.

Good luck!

Thanks a lot!