You need to have Shazam installed i think.
I have and get this working somewhat now. Didn't work before I installed it though. Sometimes it hangs and tells me Im listening to the previous song I shazamed though. Even prompts if I wanna open it in Rdio.
Edit: Okay Im an idiot. I tested this playing tunes from Rdio on my mac. Rdio was also active on my iPhone, and knew what my mac was playing, and so my phone would identify the track.
Tested using a regular radio station and nothing...
Sorry for that.