Develop native iOS apps on Windows.
Xamarin.iOS for Visual Studio allows you to develop native iOS apps on Windows, with a paired Mac providing build services over the network. Xamarin provides new Visual Studio features for iOS development, including an iOS toolbar, File > New Project for iOS apps, and iOS property pads.

Directly edit storyboards (iOS)
Double-click a storyboard file and edit it from the comfort of your favorite IDE. Drag-and-drop controls to build screens, name controls to create fields, and double-click to add handlers. No need to switch back and forth between Xcode and your source code.

More accurate than Xcode (iOS)
View controllers and controls are a pixel-perfect representation of screens as they will appear when running on iOS devices.

Live-rendered custom controls (iOS)
Unlike Xcode’s Interface Builder, the Xamarin iOS Designer renders your custom views just as easily as it renders UIKit controls–live, with custom properties editable in the properties pad.

Never touch a line of XML (Android)
Easily create Android screens by dragging controls onto the app builder, and configuring them using the properties pad. No need to get your hands dirty with XML.

Design multiple resolutions at once (Android)
Programming Android apps isn’t easy, but the Xamarin Android Designer simplifies things by previewing layouts across multiple screen resolutions and device form factors simultaneously.

Perfect property editing (iOS and Android)
Quickly configure the appearance, layout, field names, and event handlers for controls and views using a sleek properties pad.

Use the tools you know and love.
Stay productive by continuing to leverage the entire Microsoft ecosystem, including ReSharper, Team Foundation Server (TFS), TeamCity, Jenkins and your favorite code coverage and profiling tools.

Debug like a pro.
Track down bugs using the full power of a modern debugger, which can debug your app whether it's running in a simulator, or live on-device. Set breakpoints, step through code and watch values change during execution.

Award-winning features.
Microsoft awarded Xamarin the VSIP Modern Application Partner of the Year in August 2013. Xamarin is also winner of the Visual Studio Magazine 2013 Readers Choice award.

More info - https://developer.xamarin.com/releases/vs/xamarin.vs_4/xamarin.vs_4.0/