http://www.undersound.org/

«Undersound is a new type of experience, an interface that is on your mobile phone and in the underground stations you pass through every day.[…] undersound will be spatially distributed at individual stations and throughout the wider tube network. I can add music to the system at upload points in the ticket halls , and I can download tracks on the platforms. Architectural configuration of the stations affects my experience of contributing and downloading music as the proximal nature of the interaction with these situated points require s myself and other undersound users to congregate at certain locations within the station for the purpose of interacting with the system […] Because the system will be gathering metadata on the stations where the track has been (via uploading/downloading at the transfer points) and thus its spread within the network, the time it has been in the system, the number of times it has been played, the number of people who have played it, and so on, I will be able to see this information when I look at other people’s music […] Every time I listen to a track, drop one off at transfer point or download music from someone else, I have an effect on the overall state of the system. Not only is this reflected in the rankings of the tracks that I see as I browse through the lists of available music from download points and people’s mobile phones but it will also be incorporated into public displays which are installed in each of the stations […]».

Via: www.newscientist.com/