You might remember Klimper, the developer describes it as:
Klimper is a mobile music creation studio with inspiring music theory features that helps you create and develop ideas while making complex songwriting tasks easy.
- Support for Instrument Apps via Inter-App-Audio and Audio Unit Extensions
- Grouping Feature to build and arrange whole song parts easily
- New UI color scheme
- New Getting Started Tutorial
- Lots of internal improvements and bugfixes
The developer also says that support is on the way for Ableton Link, Audiobus 3 and MIDI Out. All of which will be very handy indeed.