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 StoreAudiobus is the app that makes the rest of your setup better.
Comments
I would but my tin foil hat is three layers thick
It's great but don't expect that existing apps will be easily ported. Only that from some moment on, developer's would be able to much easier develop for all platforma using one codebase.
Maybe I'm mistaken, but I believe the emphasis will be for development:
Write the app once, but it works on the various platforms
It will make things easier for development (or harder), but won't necessarily mean that iOS apps will run on OSX or vice versa. I could be wrong, but that's my understanding from my brief skimming of the announcement.