Software that tracks people on social media created by defence firm | World news | The Guardian

Riot can display on a spider diagram the associations and relationships between individuals online by looking at who they have communicated with over Twitter. It can also mine data from Facebook and sift GPS location information from Foursquare, a mobile phone app used by more than 25 million people to alert friends of their whereabouts. The Foursquare data can be used to display, in graph form, the top 10 places visited by tracked individuals and the times at which they visited them.
The video shows that Nick, who posts his location regularly on Foursquare, visits a gym frequently at 6am early each week. Urch quips: "So if you ever did want to try to get hold of Nick, or maybe get hold of his laptop, you might want to visit the gym at 6am on a Monday."