Official English Site
iTunes link
My iPod Touch is unfortunately too old to try this out, but if you have an iOS device that can run firmware version 4.2 or higher, you can get this game for free. To quote Square Enix regarding the production talent:
This card battle game is made to be free to play from beginning to end, but they intend to introduce premium paid content for it as well.The Guardian Cross development team includes top-notch talent from the FINAL FANTASY series, including Hiroyuki Ito, creator of the Active Time Battle (ATB) system.
- Original Concept: Hiroyuki Ito (FINAL FANTASY IV, V, VI, VIII, IX, XII, FFT and more)
- Composer: Naoshi Mizuta (FINAL FANTASY X-2, FINAL FANTASY XI)
- Character Design: Akira Oguro (FINAL FANTASY IV: The After Years, FINAL FANTASY Dimensions)
If nothing else, check out the official site above to get a taste of the music.