Cloud App Spotlight:
iCloud stores your music, photos, documents, or other files wirelessly and pushes them to all of your devices. iCloud is seamlessly integrated into your apps, so you can access your content on all your devices. And it's a prat of iOS 5.
Apple's iCloud uses their iCloud Storage API to enable the applications on iOS to store documents, files, and other key data onto the iCloud storage service. iCloud can wirelessly push documents to a user's device automatically and update the documents when changed on any device -- automatically. This can all be done using the APIs provided via the iOS and Mac Developer Program.