I got an Alesis IO Dock for my iPad.
It’s a pro audio dock that has two inputs and I’m hoping that I can use it with my Chapman Stick. Initial experiments indicate that it all depends on the apps.
I got AmpKit+ to give me a good sound on the melody side and Garageband for iPad to process the bass side. It appears that only Garageband can get input from the second channel. I think this will change as more people get the IO Dock and competing products come out.
Update: I took this back since almost no apps are capable of using two channels at this time. It’s also only 16 bit and I wanted 24.