Responding to more than a year of pressure, Google and Microsoft will follow Apple in adding an anti-theft "kill switch" to their smartphone operating systems, U.S. law enforcement officials will announce later Thursday. The commitment will be disclosed alongside new data that shows a dramatic drop in theft of Apple iPhones and iPads after the September 2013 introduction of iOS 7, which included a kill-switch function that allows stolen devices to be remotely locked and deleted so they become useless.