Global-positioning systems, called GPS, and other technologies used by phone companies have unexpectedly made it easier for abusers to track their victims. A U.S. Justice Department report last year estimated that more than 25,000 adults in the U.S. are victims of GPS stalking annually, including by cellphone.

Craig Thompson, Retina-X's operations director, says the software is meant to allow parents to track their kids and companies to keep tabs on phones their employees use. He ...