There is another chess variant in the iTunes store - can't remember the name. There are not that many. 
ChessQueens Variant Review
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Enjoy...
http://www.youtube.com/watch?v=5lmUHvvkTXw
I have found out that chess variants are a great way to enhance one's chess playing skills because of their unusual approaches. One really good variant that teaches strong positional play, tactical and strategic sacrificing along with solid end game is ChessQueens for the iPhone.
There is nothing like 30 queens duking it out on the chess board. :-)