Fantastic Media Lab Europe project: TunA [via Purse Lip Square Jaw] is "a mobile wireless application that allows users to share their music locally through handheld devices. Users can 'tune in' to other nearby tunA music players and listen to what someone else is listening to". What's more explicit in the paper (TunA: A Mobile Music Experience to Foster Local Interactions [pdf]) - and what I really like - is that it's targeted to a. build social capital through micro [subtle, non intrusive] interactions, and b. strengthen existing social links instead of just forming new ones. This is spot on -- technology is rarely built to work better with friends than indiscriminately with friends and strangers unless there's a technogical limit that forces the issue (eg buddylists cause IM to work better with friends).
We've talked about the tech side of this idea before so it's wonderful to see it being done. Backtrace: Dan Hill on wireless, pervasive music sharing (and glowing jackets) refs Chris Heathcote on instant psychogeographic radio refs Philip Greenspun on transparently sharing music libraries.