AppDelegate.cs

using System;
using System.Collections.Generic;
using System.Linq;

using MonoTouch.Foundation;
using MonoTouch.UIKit;

using Xamarin.Forms;

using Parse;

namespace XamarinTest1.iOS
{
	[Register ("AppDelegate")]
	public partial class AppDelegate : UIApplicationDelegate
	{
		UIWindow window;
		ParseObject currentInstallation;

		public override bool FinishedLaunching (UIApplication app, NSDictionary options)
		{
			Forms.Init ();

			window = new UIWindow (UIScreen.MainScreen.Bounds);
			
			window.RootViewController = App.GetMainPage ().CreateViewController ();
			window.MakeKeyAndVisible ();

			ParseClient.Initialize("app id here",
				"NET client key here");

			var data = NSUserDefaults.StandardUserDefaults;
			var storedInstallation = data.StringForKey ("currentInstallation");
			if (storedInstallation != null) {
				currentInstallation = ParseObject.CreateWithoutData ("_Installation", storedInstallation);
			}
			if (currentInstallation == null) {
				if (UIApplication.SharedApplication.RespondsToSelector (new MonoTouch.ObjCRuntime.Selector ("registerUserNotificationSettings:"))) {
					// iOS8
					UIUserNotificationSettings settings = UIUserNotificationSettings.GetSettingsForTypes(UIUserNotificationType.Badge | UIUserNotificationType.Sound | UIUserNotificationType.Alert, new NSSet());
					app.RegisterUserNotificationSettings (settings);
					app.RegisterForRemoteNotifications ();
				} else {
					// iOS7
					UIRemoteNotificationType notificationTypes = UIRemoteNotificationType.Alert | UIRemoteNotificationType.Badge;
					app.RegisterForRemoteNotificationTypes (notificationTypes);
				}
			}
			return true;
		}
	
		public override void RegisteredForRemoteNotifications (
			UIApplication application, NSData deviceToken)
		{

			Console.WriteLine ("RegisteredForRemoteNotifications");
			ParseObject obj = new ParseObject ("_Installation");
			string dt = deviceToken.ToString ().Replace ("<", "").Replace (">", "").Replace (" ", "");
			obj["deviceToken"] = dt;
			obj["deviceType"] = "ios";
			obj["appIdentifier"] = "com.your.bundle";
			obj["timeZone"] = "UTC";
			obj["appName"] = "YourAppName";
			obj["appVersion"] = "1.0.0";
			obj["parseVersion"] = "1.3.0";
			obj.SaveAsync ().ContinueWith (t => {
				if (t.IsFaulted) {
					using (IEnumerator<System.Exception> enumerator = t.Exception.InnerExceptions.GetEnumerator()) {
						if (enumerator.MoveNext()) {
							ParseException error = (ParseException) enumerator.Current;
							Console.WriteLine (error.Message);
						}
					}
				} else {
					Console.WriteLine("Saved/Retrieved Installation");
					var data = NSUserDefaults.StandardUserDefaults;
					data.SetString ("currentInstallation", obj.ObjectId);
				}
			});
		}

		public override void FailedToRegisterForRemoteNotifications (UIApplication application, NSError error)
		{
			Console.WriteLine (error.Description);
		}
			
	}
}