Just a brief thought on Preservation & Restoration API. It occurred to me that extending this technology to Mac OS might give us much more seamless experience when switching between apps on Mac OS and iOS apps.
Possible applications are:
There is a partial solution provided by iCloud, but it requires time to sync. The major difference of this approach is you are giving an explicit cue to the app through the UI: move my state now to a particular client (ocontrary to the continues syncing that iCloud does). Obviously it implies your interface and data being highly decoupled. Obviously it requires finding a common denominator between two platforms functionalities.
Update One of those cases when Apple introduced API serving the same purpose but implemented with Bluetooth LTE