IK Multimedia sure is workin' the iOS accessory scene hard; it has the original iRig guitar interface, the iRig Mic - and now, there's iRig MIDI, a dock connector-to-MIDI interface for iPhone/iPod and iPad.
This'll work with any MIDI-compatible app, including IK's free iRig MIDI Recorder app, and new Sampletank iOS, which is available in free and pay versions.
As long as you've got some MIDI apps and hardware, setting this thing up is simple. For our test, we used the iRig MIDI to send MIDI notes and CCs from TouchOSC on an iPhone, to GarageBand, Animoog, and other music apps, running on an iPad sitting in the Alesis IO Dock, which has 5-pin MIDI in and out jacks. Seems like a perverse setup somehow, but it worked!Read more about IK iRig MIDI at MusicRadar.com
The iRig MIDI is easy to use, highly versatile and with mini USB power while you use it, is one step ahead of the pack.