Xamarin and C# Cloud Connected Cross-Platform Mobile apps
Building cross-platform native UIs with one shared codebase was once just a dream; with Xamarin.Forms this dream is now a reality. Xamarin Developer Evangelist James Montemagno shows how to build a shared user interface completely in XAML that targets iOS, Android, and Windows all while leveraging the .NET framework to build a shared business logic backend for the apps. Additionally, you will see Xamarin.Forms additional features including built-in two-way data binding, dependency service to help you implement platform-specific code, an advanced cross-platform animation system, support for custom controls, and lots of other powerful features to help you build the best apps possible in the least amount of time. Best of all, Xamarin features deep integration with Visual Studio 2015 so you never have to leave your development environment to target all platforms. Visit http://xamarin.com to get started today.
I think that xamarin is very expensive for single developers.