Here's my cover of Joe Satriani's classic done entirely on iPad Garageband and the new features from the 1.2 update. All played instruments are native to the app.
The added features like the note editor and within song key change expands the usability of this app greatly. Now, you have access to the guitar's whole range by transposing notes which made this cover possible. This song has a major to minor key change so this was almost impossible with the old version of GB.
It is now viable to play any guitar part but it requires a bit of editing work as you could see on this video. Most of the edits I did on the guitar track are for the vibrato and the octave transpositions. It is hard to get a consistent vibrato in real time because of the touchscreen. Also, although I'm playing along in this video, the actual guitar track was recorded in parts and some tricks were used. The video is just to give you an idea where the notes are and how I played them.
Key is B Major/ Minor
Time Sig: 3/4
Tempo: 147 BPM
Scales used: None, B Major, B Minor, B Pentatonic Major
Main Guitar Sound: Hard Rock with Vintage Drive
2nd Guitar: Roots Rock with Hi-Drive and muted (Finger on the "Nut")
Classic Drum Machine
Large Hall Reverb
I hope this will give you ideas for your iPad GarageBand noodlings.