gistfile1.txt

using System;
using ReactiveUI;
using System.Windows.Input;
using System.Threading;
using System.Threading.Tasks;

namespace RxUITestApp
{
    public class MainVM : ReactiveObject
    {
        public ICommand HelloButton { get; private set; }

        public MainVM()
        {
            HelloButton = ReactiveCommand.CreateAsyncTask(async _ => {
                await Task.Run(() => {
                    Console.WriteLine("About to sleep!");
                    Thread.Sleep(5000);
                    Console.WriteLine("Done sleeping!");
                });
            });
        }
    }
}

// ===

using System;
using System.Drawing;

using MonoTouch.Foundation;
using MonoTouch.UIKit;

using ReactiveUI;
using System.ComponentModel;

namespace RxUITestApp
{
    public partial class RxUITestAppViewController : ReactiveViewController, IViewFor<MainVM>
    {
        public MainVM ViewModel {
            get;
            set;
        }

        object IViewFor.ViewModel {
            get {
                return ViewModel;
            }
            set {
                ViewModel = value as MainVM;
            }
        }

        public RxUITestAppViewController(IntPtr handle) : base(handle)
        {
            this.ViewModel = new MainVM();
            this.BindCommand(ViewModel, x => x.HelloButton, x => x.btnHello);
        }
        
        //...
      }
    }
  }
}