iOS introduced a way for users to transfer files from an app to a computer via iTunes.

It is simply adding a UIFileSharingEnabled to info.plist. There is a very small introduction here.

When you enable file sharing, ALL files in <Application_Home>/Documents will be shared.

Users can copy files to and from the app, as well as delete.

So be cautious of that.

You might also want to monitor the directory. There is a way to do that using kqueue().