Adding a "Like Us on Facebook" button to a mobile app

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http://stackoverflow.com – A lot of mobile apps have a "Like Us on Facebook" button that directs the user to a Facebook fan page. In mobile games, liking the fan page rewards the player in some manner. If I simply open a web view with my game's Facebook fan page, I won't know if the user liked my page when he returns to the game. He might not have even logged into Facebook. How can I make sure the user liked my Facebook page? (I've seen games that check that) BTW, I'm working with MOAI, but a native iOS or Android solution would also be a great help. Thanks! (HowTos)