Not a portable sauna, this is me in a BodPod, about to get my % body fat measured. A little quick research led to this as the modality of choice: it's what the NFL uses, it uses no radiation (unlike the DEXA method), and it's pretty inexpensive ($20-35 a pop). A pair of close fitting bike shorts and a swimming cap (provided, to negate any air pockets that might stilt the results), and I was good to go.
This is a unit in the Kinesiology Department at Vanguard University -- courtesy of the find-a-unit-near-you section of BodPod's website.
Looks like something out of 2001...or Sleeper.
Special thanks to department head Diana Avans, who kept me in stitches while running the test. It takes about 5-10 minutes if you're not laughing your head off.
Results: 23.8% body fat, with a very accurate weight of 203.445 lbs.
That's 48.447 lbs of fat. A lot of room for improvement, but that's the whole point: establishing a reliable baseline, so significant progress can be tracked.
Even if you have the most accurate bathroom scale, your readings will go up and down with water, poop in your gut, state of bladder emptying, and fat and muscle. With refined methods like the BodPod, you can reliably track when your fat weight goes down, and your muscle mass (hopefully) goes up.