Chinese authorities are now using the tools of big data to detect departures from “normal” behavior among Muslims in the country’s Xinjiang region—and then to identify each supposed deviant for further state attention. The Egyptian government plans to relocate from Cairo later this year to a still-unnamed new capital that will have, as the project’s spokesman put it, “cameras and sensors everywhere,” with “a command center to control the entire city.” Moscow already has some 5,000 cameras installed with facial-recognition technology, and it can match faces of interest to the Russian state to photos from passport databases,...