Taking advantage of background multi-tasking in iOS 4
Your Program must inherit from MonoGameProgram and assign the new instance of your Game. See the example below....
class Program : MonoGameProgram
public override bool FinishedLaunching (UIApplication app, NSDictionary options)
// Fun begins..
MonoGameGame = new MyAwesomeGame();
static void Main (string  args)
Then the XNA Activated and Deactivated events will be called when DidEnterBackground and WillEnterForeground are called.