First impressions: Well, initially, I didn't really know what to do... some sort of explanation would definitely be helpful (maybe brought up by hitting the "power play" button at the top). Also, I would recommend against using the UITabBar for selection or control, as it is generally associated with completely separate views. It should at least be styled differently, so that people don't think of it like, for example, the clock app. This relates to the settings selection... you can select it, and then remove the view with 'x', but settings is still highlighted. Finally, I'd recommend adding background audio support and better resume from close functionality.

Just my 2c, overall its a well executed app.