Camel Audio released Alchemy Mobile, a free app for the ipad/iphone. Alchemy Mobile is a smaler version of their famous Alchemy VSTi plugin. The GUI and usage is quite good and you can upgrade the app to a pro version that can control Alchemy.
“Turn your iPhone/iPad into a powerful synthesizer! Alchemy Mobile includes everything from evolving soundscapes and fat basses to lush pads and pulsing arpeggios, and is available for free from the iTunes App store. This is the iOS version of Camel Audio’s award-winning Mac/PC Alchemy synth – the leading sample manipulation synthesizer which can be heard on thousands of records and films by world-class artists.
Touch Remote for Alchemy on Mac/PC
With the Pro Upgrade ($19.99/€15.99/£13.99), you can remotely control Alchemy or the free Alchemy Player on your desktop computer. This is the first iPhone App to offer a dedicated touch remote feature for a desktop synth! Easy one touch access to the remix pad and preset selection means you’ll spend more time getting inspired and less time reaching for your mouse.”
More info here: http://www.camelaudio.com/AlchemyMobile.php
free download here: http://itunes.apple.com/de/app/alchemy-synth-mobile/id432505977?mt=8