Relay runners all over the world 'pass it on' via email and their races are tracked online in Nike RUN Fwd, an interactive project from Nike Japan.
The idea is based on Ekiden, a popular Japanese winter sport in which long-distance relay runners pass on a sash called a tasuki instead of a baton.
In Nike's version, participants must run at least 3km of the race and then nominate the next runner in their team via email invitation. The email contains a customized movie showing who has run so far and asking if they're willing to take up the challenge. If they fail to run within the allotted time period of 72 hours, the team will be disqualified. Teams compete over the two month race period as they contend to become the world's longest Ekiden team.
The runners are tracked using Nike+GPS and their running routes recorded online, with map information played as a movie showing the journey of the sash around the world.