Mattias Östergren from the Interactive Institute in Stockholm has developed SoundPryer, a wireless peer-to-peer software for mobile music “socials” in cars. Each driver becomes a mobile radio station, transmitting their digital music stream to other cars within Wi-Fi range. It enables music eavesdropping in traffic encounters, by streaming MP3 files via the Real Time Protocol.

How it works: you attach a PDA, with built-in Wi-Fi card, to the dashboard and starts the Sound Pryer application and play Chopin on the car stereo. Suddenly, the icon of, for example, a red lorry appears on the screen and a tune from J-Lo fills your loudspeakers. Sound Pryer returns to playing your own music after you’ve passed the lorry.

More details in the PDF.
Via Networked_performance < the Feature who draws parallels between SoundPryer and the tUNA project of Media Lab Europe.