I was turned on to this app via the great site, ReadWriteWeb. Band Metrics is currently in private Beta, but is soon to open up. It will allow bands...or composers...to track how their music is doing online: who's listening and sharing your music via social networks, who's talking about your music and so on. Some great potential here. You can head over to ReadWriteWeb for a bit more info and screenshots or you can go directly to Band Metrics and register for an invite.