Desktop widget that integrates with WP?

How difficult would it be to build a desktop widget (either with the Yahoo or Google widget engine) that sits on the desktop and displays the latest X number of posts from a particular blog? Not just any blog – it would be tied to a specific blog, for branding purposes (i.e. the look/feel of the widget would have to be modifiable, to look just like the blog).

Does this exist, to anyone’s knowledge? Would it be hard to do?