Desktop Widget (Mac and PC)

I need to have a desktop widget created for our clients. I've been told AIR is the way to build them. It needs to be able to work with xml from our server to update, etc. We will have 5-10 different designs for the widgets which our clients can pick from and then they can sell advertising, etc. My php programmers will help create a backend so the clients can update the widget. Widget I assume can include RSS feeds, Hot stories, etc. I also need the widget to be able to flip to show more information.