The arrests spurred a splash of publicity from state media, who are crowning Mr. Cheung--one of the Hong Kong megastars known as the "Four Heavenly Kings"--with a new title: "The Nemesis of Fugitives." China's police departments have been openly touting their use of technology to nab lawbreakers--a campaign that rights activists say is aimed at winning public support for growing state surveillance. Concert organizers in China have also increasingly deployed facial-recognition systems to curb scalping by verifying the identities of ticket-holders. Surveillance companies and local security agencies have experimented with deploying the technology at events around the country in recent years. The tests date back to 2015, when one company, Shenzhen-based Firs Technology Co. Ltd. said its facial-recognition system helped police identify drug-users, fugitives and ex-convicts at a jewelry exhibition in the city of Chenzhou, in central China's Hunan province.