Accidentally deleted app (plus its data)

Yesterday evening I put my iPhone 4 in my pocket and kept my hand there for a while. I guess I didn't lock the screen, as I drew it back, an app was disappeared from the home screen. No problem for the app, which can be redownloaded: the problem is represented by its data.

In fact deleting an app, even accidentally, erases all the data associated with it, which can be recovered from a backup. I've got a couple of recent backups: one on my Mac and one on iCloud. The thing is, as far as I know, that the restore from backup features is an "all or nothing" action: one must restore the whole device but not a single app (which I find not very good).

Does anyone know how to restore only those data associated with the deleted app? I extracted the files from the Mac backup but they're xml, perhaps crypted, and unreadable (it would be enough to read the informations on them: I don't need the file itself).

I thought of restoring this last backup on my old iPhone, but the latter doesn't support iOS 5, thus I guess iTunes won't do it. Note that the old iPhone was jailbroken: would it be possibile to copy the backed up files in the application folder? I know it doesn't sound a great solution, but better than nothing!