IPhone/IPad App using XMLRPC or SOAP

Looking for a developer to write an IPhone/IPad application to connect to our application using XMLRPC or SOAP. This application needs to work on IPhone, IPad, Android and Windows Phone. A cross platform technology like Xamarin is preferred. Technology is open for suggestion, but must be approved. Artwork will be supplied initially, but may change. A working windows application will be supplied with all functionally working that is required. The application will consist of 15 screens, not including a Facebook login. The back end system allows XMLRPC or SOAP to access the required data. As new versions come out, the developer may be asked to make changes on an hourly paid basis. This application will be open to the public after beta testing is complete.