I would like to develop an app (mobile/Windows/Mac) which accesses several cloud storage sites and lists all files and folders in a single list. The user would be able to connect to their accounts on DropBox, iCloud, SkyDrive, Box, Google Drive, etc. and view ALL of the files in one list. The list would appear as though the files are in one single location. Folders could contain files which are spread out on any of the cloud storage services.
On the desktop, the app would display a single folder structure with all files synced locally, on the workstation.
On Mobile: The app would interact with other mobile apps for viewing various file types. i.e. a spread sheet would be viewable in Numbers on iOS or a pdf would open as it would otherwise, photos could be saved locally or opened in editing apps.
The app would assist users in signing up for multiple accounts and would store their username/password locally, in the mobile or desktop.