Music Navigation Gadget

I have a Sony Walkman phone and navigating my music is an entirely unpleasant experience. Therefore imagine my excitement when I read the following link title sent to me by my design minion. Rotary Style Music Navigation. This is stunning to look at and nice idea in theory but unless it stores music itself why would you carry around another gadget just to nav your music?

If you know the answer please let us know in the comments.