Play hundreds of instruments, samples, effects and loops – on your acoustic guitar. ACPAD puts an electronic orchestra in your hands!
Found this on Kickstarter and while it's not iOS specific, the demo video mentions support for Mobile and it seems like a great match!
Essentially it's a giant 'pickguard' which attaches non-destructively to your favorite acoustic guitar and provides wireless enabled pads and controls to play other apps via MIDI. It's not a guitar-MIDI note converter, instead it provides ergonomically positioned controls to trigger samples. loops, drums or whatever, while playing the acoustic instrument.
Anyone who has ever attempted a solo coffee shop performance with a guitar, drum machine, a couple of pedals ( and yes, back in the day even cassette drum backing ... don't ask... ) might find the idea of a control panel of sounds where they need to be, rather than under a tangle of wires in the dark, intriguing. Take a look at the video.
The buy-in from Kickstarter is about $300US and it's way over funded so hopefully this will turn into a real thing. Can't wait to read some reviews!'