Nick Randolph wrote a good example of utilizing ASP.NET AJAX 4 (pre-release), ADO.NET Entity Framework, and ADO.NET Data Services to create Windows Mobile 6.5 Widget that exposes data from SQL Server database.
http://community.softteq.com/blogs/nick/archive/2009/06/10/accessing-data-with-windows-mobile-6-5-widgets-ajax-4-entity-framework-and-ado-net-data-services.aspx