"I can't turn it on, for legal reasons, but if I did, mobile phones in this room would die within seconds," says Michael Menage of Global Gadget UK.
Every cell phone within 200 feet flatlines, including important emergency calls, which is why jammers are illegal to have.
But, as CBS News Correspondent Sharyn Alfonsi reports, when CBS went undercover, posing as nightclub owners into a New York City spy shop, it became apparent that they're pretty easy to buy.
When we asked if one could be obtained within 24 hours, we were told, "Yeah, just tell me when you want it, and I'll get it for you."
Moments later, a jammer was purchased out of the back room for $2,000.
For a lot less, you can order them online from companies overseas. Menage says more than 2,000 of the jammers he sells every year are shipped to the United States.
"I would say most of our customers are just people who are cheesed-off by people using mobile telephones indiscreetly," says Menage. "Then there is the business sector."
Restaurants, casinos, even churches are buying jammers. But the FCC says, it amounts to stealing, saying cell phone users pay good money to access the airwaves.
"The penalties are huge if you get caught," says Rob Bernstein of Sync Magazine. "Just having a cell phone jammer can cost you $11,000 and a year in prison."
But the thing is, no one has been caught. Most people don't even know they've been jammed.
So the next time your call drops out, think twice. Someone might have been sick of your lip and just made you "shut the cell up."