A Minnesota entrepreneur named Kirk Kjellberg has generated a lot of Internet traffic with his proposed Ideal Conceal Pistol, which resembles a mobile phone until the user clicks a safety, causing a handle to swing down and revealing a trigger. In gun mode, the device has two barrels that each fire a .380-caliber bullet. It's supposed to be a derringer for the digital age.

In an interview, the voluble Kjellberg explains that his aha moment came on the way to the men's room in a restaurant. A little boy noticed the handgun, legally if imperfectly concealed beneath Kjellberg's jacket. "Mommy, that guy's got a gun!" the boy shouted. "Everyone turned to look, and it caused a lot of fuss," Kjellberg says. "I thought to myself there has to be a better way."

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