I recently purchased a Griffin Guitar Connect cable for the iPhone and I've recorded a couple short clips in GarageBand with it. This is the easiest and most fun time I've had with recording. The smart drums feature is sweet. In in just a few seconds you can come up with a basic drum beat to use as a scratch track sort of thing.
I run my Blackstar's recording output directly into the iPhone and it's damned awesome. I have the clips on Soundcloud, but I am at work, so I'll post them up later.
Just wanted to say...this is awesome...
Need. GarageBand. For. Iphone. Now.
I use it on my Macbook, but it's so much better on the Ipad.