With this library you can build HTML 5 Widgets app as a native WP7 app, which you can publish on the windows phone marketplace and easily make update for the app. Widgets for WP also tries to solve problems involved with running an HTML page in offline mode on Windows Phone. The library installs the HTML5 content in isolated storage by simulating the real hard disk and paths of the HTML pages, scripts, images etc. -- Bahrudin Hrnjica
The library also works well for creating Native/Web hybrid apps, which are an emerging trend these days. Check out the CodePlex page to give it a whirl and see how it works.