MultitrackStudio for iPad is the first AU host for iOS!

So here's what's new in MultitrackStudio for iPad:

• Supports iOS 9 Audio Unit effects and MIDI instruments. Note: presets and automation are currently not supported.
• Some bug fixes.

Of course it says "presets and automation are currently not supported", which suggests that they will be at some point in the future, which is og course great news too.