I recently wrote an article with my friend and colleague Bruno Terkaly for MSDN magazine on using Windows Azure to support mobile device applications (including iOS, Android, and Windows Phone) that require back-end services. The solution that we propose is based on a REST style architecture, a very popular approach that provides flexibility and speed. I hope that you enjoy it and find it useful.
Here is the link: http://msdn.microsoft.com/en-us/magazine/hh781021.aspx.