Cloud Mate
I have not yet explained how on earth Cloud Mate on iOS is able to show you a preview of the contents of an iCloud-based file, as well as handing that file off to various other apps and services. The answer is that Cloud Mate’s information about each cloud-based document includes not only its name, size, and modification date, but also the URL of its storage location at www.icloud.com. Thus, when you tap on the name of a document, Cloud Mate does effectively the same thing that Dropbox does when you tap on the name of a document in the Dropbox app — it downloads the document from iCloud!
The iOS app is possible because the companion Mac app is not sandboxed.
