iCloud without the Internet I know this is a long shot, but is there any way of using icloud or parts of it for syncing between two devices in physical proximity (using Bluetooth or ad hoc wifi) but without a connection to the Internet?

Or maybe a better question is: are there any apps (jailbreak or otherwise) that enable similar features to icloud without an Internet connection?
Syncing devices without iCloud won't work, because the data flow is like that: device1 -> iCloud server -> device2. The device sends data to the iCloud server, and the second device grabs this data from the same. The iCloud server is also responsible to keep the version history straight.

So if you want to sync data between an iOS and Mac OS device, you can do everything over Wifi in iTunes (Apps, in-App data, music, videos, calendar ...). You might also want to take a look at Files App for iOS. This app is a Mac OS Finder-like data management program that allows easy sync between iOS and Mac OS: it temporarily opens a network port and you can push data to the iOS device from your web browser without internet connection. 

And if you want to sync Data between two Mac OS devices (MacBooks or iMacs), you could simply use Dropbox's LAN Sync, which does not require a internet connection as long as both computers are connected to the same network. Depending on what you want to sync, you could simply but you data there, e.g., to sync you calendar, simply write and write the .ical file to Dropbox.