SpriteBuilder allows you to build your game for both the iOS as well as Android platforms. Currently, it only supports Objective-C, although Swift support is in development.

However, you will need an Android device to run your project as an emulator is not supported to test android builds. It is also recommended that you buy a branded phone for testing purposes. You could get a Nexus or a Samsung series phone or tablet as they are widely used and well supported.

Also, to run the project, do not use the latest version of Xcode as the SpriteBuilder Android plugin doesn't support it at the moment. Instead, use Xcode version 6.1.1. It can be downloaded from http://developer.apple.com/downloads/.

The good thing is that you don't need the Android SDK to build on Android. You can run the code sitting in the Xcode environment.

However, this being said, if you want to implement InApp purchases or Leaderboards and Achievements, you would have to code separately for the iOS and Android devices as implementing on one won't make it run automatically on the other platform.