Reader marlow77 pointed out the recently released MIDI Guitar app. This Guitar to MIDI converter is similar to Audio MIDI Connect, offering WiFi MIDI, CoreMIDI and Virtual MIDI.In fact it is so similar to Audio MIDI Connect, I asked marlow77 what he thought of the two. Here is his synopsis:
Audio MIDI Connect is great, but it doesn't have polyphony. Both are pretty comparable when they are in mono mode, except that Audio MIDI Connect does allow recording and then converting to midi and DSMIDI WiFi compatibility. Also MIDI Guitar has a great sensitivity control that helps control polyphony chaos under some conditions.
MIDI Guitar is most effective with 3-4 note chords. However it does seem to be pretty CPU intesive because some apps struggle in the background. Surprisingly, Addictive worked very well in the background with Midi Guitar on my Ipad 1.
The app is free. To actually use the MIDI it is converting though, you'll need to cough up for an In App Purchase. The current price of the IAP is $5, but the iTunes description says it is 75% off, so I assume that will go up to $20 in a hurry! Without the IAP it will only play internal Piano samples.
There is a brief demo video from the developer. He notes that it works best with a guitar interface connected to your iDevice.