According to this article, the system works by simulating 3D audio from your cell phone so you feel like the person at the other end of the call is actually in front of you. Both joggers would be linked via cell phone and GPS, running in two different physical locations but in the same virtual "race" together. If one jogger gets ahead of the other, their voice appears to be coming from in front of you, motivating you to speed up and catch-up with the other runner.