Fernando Figueiredo, Bullet’s president, said the GPS device is activated when a shopper removes the detergent carton from the supermarket shelf. Fifty Omo boxes implanted with GPS devices have been scattered around Brazil, and Mr. Figueiredo has teams in 35 Brazilian cities ready to leap into action when a box is activated. The nearest team can reach the shopper’s home "within hours or days," and if they’re really close by, "they may get to your house as soon as you do," he said.