ITAMI, Japan — In his early 70s, Koji Uchida began to vanish.The first time, the police found him sitting in front of a vending machine 17 miles from home. He began to go missing regularly, once wandering for two days before turning up at a stranger’s apartment, hungry and barely able to remember his name, his mind clouded by dementia.At a loss for what to do, his family asked the local government to put Mr. Uchida under digital surveillance.In Itami, the suburb of Osaka where Mr. Uchida’s family lives, more than 1,000 sensors line the streets, each unit emblazoned with a smiling cartoon figure bracketed by Wi-Fi squiggles. When Mr. Uchida went out walking, the system recorded his location through a beacon hidden in his wallet and se …
