monotouch compass overlaying mapview

I need to display a small compass over the mapview.

Is there a standard way of ach开发者_JAVA百科ieving this? It obv needs to update as the direction the phone is pointed in changes.

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As of iOS 4.2, there doesn't appear to be a standard way to display a compass on an MKMapView.

http://developer.apple.com/library/ios/documentation/MapKit/Reference/MKMapView_Class/MKMapView/MKMapView.html