We have to use Parse Android SDK binding in a Xamarin.Android app to use the Parse push notification. It took a week to get the push working till we found need to use the package name as the namespace of our custom push receiver class!
Parse Android doc: https://parse.com/tutorials/android-push-notifications
Custom Receiver reference: http://stackoverflow.com/questions/26154855/exception-when-opening-parse-push-notification
Java package name V.S. C# namespace: http://www.javacamp.org/javavscsharp/namespace.html