Audiobus: Use your music apps together.
What is Audiobus? — Audiobus is an award-winning music app for iPhone and iPad which lets you use your other music apps together. Chain effects on your favourite synth, run the output of apps or Audio Units into an app like GarageBand or Loopy, or select a different audio interface output for each app. Route MIDI between apps — drive a synth from a MIDI sequencer, or add an arpeggiator to your MIDI keyboard — or sync with your external MIDI gear. And control your entire setup from a MIDI controller.Download on the App Store
Audiobus is the app that makes the rest of your setup better.
Rocksmith USB Tone Cable as guitar “interface”
Not sure if this is well known but I recently discovered that you can use the Rocksmith RealTone USB cable combined with the CCK. It’s a 1/4” to USB cable that is used for the Rocksmith game, but it is a very fast way to connect a guitar to your iPhone/iPad. I’m not prepared to comment on latency etc but I didn’t really notice any issues.
It’s a pretty cheap way to connect your guitar - I think it’s about $35 USD.