PhonePresenter.cs

public class PhonePresenter : MvxTouchViewPresenter
{
	private void navigateInPlace(MvxViewModelRequest request)
	{
		var nextViewController = (UIViewController)ViewCreator.CreateView(request);
		var menuViewController = MasterNavigationController.ViewControllers.FirstOrDefault(vc => vc.GetType() == nextViewController.GetType());
		
		if (menuViewController != null)
		{
			MasterNavigationController.PopToViewController(menuViewController, true);
		}
		else
		{
			var transition = new CATransition();
			transition.Duration = 0.3;
			transition.Type = CAAnimation.TransitionPush;
			transition.Subtype = CAAnimation.TransitionFade;
			
			var exitingViewController = MasterNavigationController.TopViewController;
			
			MasterNavigationController.PopViewControllerAnimated(false);
			MasterNavigationController.View.Layer.AddAnimation (transition, null);
			MasterNavigationController.PushViewController(nextViewController, false);
			
			exitingViewController.SafeDispose();
		}
	}
}

ViewControllerBase.cs

public abstract class ViewControllerBase : MvxViewController
{
	public override void DidMoveToParentViewController(UIViewController parent)
	{
		base.DidMoveToParentViewController(parent);

		if (parent == null)
			this.SafeDispose();
	}
}

ViewControllerExtensions.cs

public static class ViewControllerExtensions
{
	public static void SafeDispose(this UIViewController viewController) 
	{
		if (viewController.ParentViewController != null)
			return;

		var mvxView = viewController as IMvxTouchView;

		if (mvxView == null)
			return;

		if (mvxView.ViewModel is IDisposable)
			((IDisposable)mvxView.ViewModel).Dispose();

		mvxView.ViewModel = null;
	}
}