SketchFlow Template for Windows Phone (downloadable from Codeplex)

The SketchFlow Template for Windows Phone 7 adds a new SketchFlow template
for Expression Blend* users that makes creating a prototype of a Windows Phone
app quick and easy.

* Please note: To use the SketchFlow Template for Windows Phone 7 you need to
be using Blend 4 with SketchFlow enabled (this is the version of Blend that
comes with both Expression Studio 4 Ultimate and Visual Studio 2010 Ultimate)
you also need to have the Mango
developer tools for Windows Phone installed.