Hey Jan,
Yes, we're G2G from the App Side (EAAccessory Framework). But, I'm now having to write the interface on the device side (uController). I've never had to do that, but am familiar with Microchip devices. I took the tutorials in your book, but it's been a while.
The part that is a bit unknown for me, is getting the device to enumerate with the phone. Our intent is to have the phone as the Host and the uController as the device. For the App side, once the device is successfully enumerated (finds an acceptable protocol) then it will appear in an array within the EAAccessory Manager. It's easy enough to search the array and open a session to begin comm. That's all fairly straightforward.
Also, I've not authenticated to an Apple device via the lightening plug. Seems we'll all probably learn a lot!
I did read a few posts in the forum regarding CDC and mimicking an AT device. My thoughts at this point is to create a CDC type connection.
Thanks!
Seth