Windows Phone 7 Global UI Element?

I'm trying to add a Global UIElement in my Windows Phone 7 app (ie. a UIElement that is shared across all pages)

Specifically, I'm trying to get the MediaElement to continue playing when I navigate to diff开发者_如何学Cerent pages.

I've tried playing with the Application.RootVisual / PhoneApplicationFrame but I can't seem to get it to work.

Add a Popup with no parent.