“George Gascón, San Francisco’s district attorney, says handset makers like Apple should be exploring new technologies that could help prevent theft. In March, he said, he met with an Apple executive, Michael Foulkes, who handles its government relations, to discuss how the company could improve its antitheft technology. But he left the meeting, he said, with no promise that Apple was working to do so. He added, “Unlike other types of crimes, this is a crime that could be easily fixed with a technological solution.” Apple declined to comment. The cellphone market is hugely lucrative, with the sale of handsets bringing in $69 billion in the United States last year, according to IDC, the research firm. Yet, thefts of smartphones keep increasing, and victims keep replacing them. In San Francisco last year, nearly half of all robberies involved a cellphone, up from 36 percent the year before; in Washington, cellphones were taken in 42 percent of robberies, a record. In New York, theft of iPhones and iPads last year accounted for 14 percent of all crimes. Some compare the epidemic of phone theft to car theft, which was a rampant problem more than a decade ago until auto manufacturers improved antitheft technology. “If you look at auto theft, it has really plummeted in this country because technology has advanced so much and the manufacturers recognize the importance of it,” said Chuck Wexler, the executive director of the Police Executive Research Forum, a nonprofit group focused on improving police techniques. “The cellphone industry has for the most part been in denial. For whatever reasons, it has been slow to move.”