Lt. Travis St. Pierre, of the New Orleans Police Department, shows off a body-worn camera during a press conference in January. Brett Duke/The Times-Picayune/Landov hide caption

itoggle caption Brett Duke/The Times-Picayune/Landov

BlueJay, a tool by social media monitoring company BrightPlanet, shows the locations of tweeters who have left their geotagging option activated. BlueJay screenshot hide caption

itoggle caption BlueJay screenshot

Protesters line up outside City Hall in Oakland, Calif., to demonstrate against the Domain Awareness Center, a data integration system being built by the city and the Port of Oakland. Martin Kaste/NPR hide caption

itoggle caption Martin Kaste/NPR