As to the value of RF protective gear, Melnick declined to offer an opinion. "That's a personal decision," he said. "I can't say with absolute certainty that there's no risk."

The Federal Trade Commission takes a more skeptical line on its Web site, saying, "[T]here is no scientific proof that the so-called shields significantly reduce exposure from electromagnetic emissions. [P]roducts that block only the earpiece -- or another small portion of the phone -- are totally ineffective because the entire phone emits electromagnetic waves. What's more, these shields may interfere with the phone's signal, cause it to draw even more power to communicate with the base station, and possibly emit more radiation."

A spokesperson for the FTC cautioned that, "There are a lot of false claims about these types of products." She said that product claims must be truthful, not misleading, and substantiated.

In 2003, the FTC won a settlement with the makers of WaveShield cell phone radiation shields, Interact Communications, that forced the company to stop making unsubstantiated claims about it product. The FTC complaint alleged "that the defendants made false statements that their products had been scientifically 'proven' and 'tested,' when in fact that was not the case."

While DeToffol dismisses competing EMF protection products from Biopro Technology as the "hand-waving" of a "multilevel marketing company," he insisted his company's products work. "The products that we sell can all be demonstrated objectively," he said. "You can show the shielding effect with a meter."