I have found this great new Gin Rummy App on the Apple ITunes Store for the iPhone or iPod Touch.
It has really good graphics and has some really good game functions. In the next few versions, it might even have multiplayer.
Link to the App on ITMS:
http://itunes.apple.com/WebObjects/MZStore.woa/wa/viewSoftware?id=304497413&mt=8
Made by: http://neuroticnerd.com/blog/