Apple just updated GarageBand for iOS to v1.4:
- Play and record music apps supported by Audiobus directly into GarageBand
- Turn off grid snapping to get finer control over region and note editing
- Fixes an issue that resulted in feedback while connecting 3rd-party audio accessories into the headphone/microphone jack
Yes, Audiobus support! That's an incredible success. Over 100 iOS audio apps added Audiobus support in just 3 months and now Apple's own GarageBand adopts the technology.