Shows off using a UIButton with a background image as a UIBarButtonItem, and handling touch events accordingly.

CustomUIBarButtonItem.cs

  		var composeButton = new UIButton (new RectangleF (0, 0, 20, 20));
		composeButton.SetBackgroundImage (Images.ComposeButton, UIControlState.Normal);
		composeButton.SetBackgroundImage (Images.ComposeButtonHighlighted, UIControlState.Highlighted);
		composeButton.AddTarget((object sender, EventArgs args) => PresentViewController (new PrayerComposeDialog (), true, null), 
			                       UIControlEvent.TouchUpInside);

		ComposeButton = new UIBarButtonItem (composeButton);

		NavigationItem.RightBarButtonItem = ComposeButton;