TimeMachine is a utility, the only utility, that enables the use of AirDisks and Network Disks in Time Machine. Even with the new release of TimeCapsule, users can still not use AirDisks with Time Machine. You can Do It with iTimeMachine.
What's New: iTimeMachine v1.1 now checks if you have network drives enabled. It also uses a toggle button instead of the old UI design. It now includes a progress indicator. It also automatically opens Up the Time Machine preference pane and gives tells the user that it has enabled AirDisks.