I got curious and called about it. There's actually two kinds out now...one is done by hand with an airbrush and the other is done by machine.
Both use a fine mist that has a DHA component in it - which is the same stuff that's in self-tanners that works with the chemistry of your skin to turn it dark. The machine is just a capsule that you walk into and shut the door. A fine mist shoots out all around you and seconds later, you're done! Thirty bucks. Last 5-7 days and completely non-toxic.
The airbrush system is done by a human being (and y'all thought it was applied by a monkey, right?). Exfoliate your own body, strip down, stand naked in front of the "artist" while she/he sprays you with an airbrush. Thirty bucks for one coat, $35 for two coats (for a deeper, darker tan). For some reason, this method lasts 7-10 days. The spray goes on clear so it won't rub off on your clothng. This is more time-intensive though and takes about 30 minutes.
What WILL they think of next?
(Well ONE thing they've thought of I discovered as I was perusing the yellow pages: A Laundry/Tanning Parlor. Their ad says "Tan While You Do Your Laundry". Actually quite a good idea. Put them in Jiffy-Lubes and you could tan while you get your oil changed.)
-frolix