It's called a "whole body imager," and it can indeed see your whole body underneath your clothing, reports CBS News correspondent Nancy Cordes.
San Francisco is one of 19 domestic airports where the scanners are deployed. Forty machines so far across the country, with 250 planned for next year, at $170,000 apiece. Passengers get to choose whether to pass through the body imager or a traditional metal detector.
"I was just pretty impressed at how quick it took, said Jared Thomas, an airline passenger. "She said two seconds - it was two seconds."
Two seconds to see whether you have something suspicious on your body, perhaps made of plastic. The worst case scenario is an improvised explosive device. When a passenger goes through, a TSA screener checks out the revealing image in another room. The passenger's face is blurred, but the body is fully exposed.
"Once that evaluation is complete, the scan is deleted, and it's gone forever," said Nico Melendez, a TSA spokesman. "So we can't capture, we can't print, we can't transmit. We don't hold the image at all."
At first, the TSA offered the body imager as an alternative to a pat down for passengers who set off a metal detector or who were selected for extra, so-called "secondary" screening. Now, in San Francisco and five other cities, the machines are an option for "primary" screening. That bothers privacy advocates.
"The technology is very invasive," said Lillie Coney, the associate director of the Electronic Privacy Information Center.
The Electronic Privacy Information Center also worries that travelers don't realize how revealing the body imagers are.
"Is this really a violation of privacy if the person who's looking at your body is locked away in a room, doesn't know who they're looking at and can't record the image?" asked Cordes.
"Absolutely! If you think about it - privacy is a very fundamental right," said Coney. "It's about the collection and use of personally identifiable information. And your unclothed body is as personal and identifiable as you can get."
But the TSA says that's just what makes the device so effective.
"It's better than the one that blows the air at you," said Kris Wafler, an airline passenger.
Those "puffer" machines - meant to detect explosive residue - are being eliminated after five years - a $36 million mistake. They kept breaking down due to dirt and humidity.
That's not an issue with whole body imagers, which don't use x-rays, but electromagnetic waves - that the TSA says, emit less energy than a cell phone.