GuitarJack 2 is a superb audio interface for your iDevice. As I have the first and the second versions of the hardware I can see how it's evolved and the design has moved forward.
And it works beautifully with the iPad and the iPhone 4/4S. Obviously the 5 is different and you need a 30 pin adapter.
GuitarJack 2 and the FourTrack software / hardware integration is very slick indeed and a big improvement on the first version.
But what really strikes you is the quality of the GuitarJack 2. Not just the external build quality, but the sound quality through the device. I can't remember where I read it, but I remember that someone had written that they thought that there was something wrong with the guitarjack when they plugged in their guitar because there was no noise, but it wasn't broken, just noiseless. Well I found that too. The line in is great too, it works very well to have a stereo in for the iPhone or iPad.
One of my main uses of the GuitarJack 2 is recording iDevice to iDevice, but you could plug anything into the GuitarJack 2 and get great sound out of it I'm sure. The quality is amazing and completely configurable within FourTrack too, which is very handy.
So whilst it would be on the expensive side of Christmas presents, I'm sure it would be very welcome.
You can find out more about the GuitarJack 2 including where to buy it via the Sonoma site.