A novel class of phone-to-phone mobile-motion games aims to achieve a level of physical interactivity comparable to Wii or Kinect games but without relying on an external infrastructure. The key underlying technology in these new mobile-motion games is a real-time phone-to-phone distance measurement substrate the authors developed 2014; the Fast, Accurate, and Robust (FAR) localization system. The system enables two potentially fast-moving phones to keep accurate distance estimates. To practically demonstrate the system's ability to enable novel gaming concepts, they developed SwordFight, a prototype mobile-motion game.