unDock

unDock is a menu item that places an "unDock Now!" command that ejects all drives connected to your Mac.

If a Time Machine backup is occurring, it will safely cancel the backup and eject the disk.
When you're ready to go, use either the keyboard shortcut (default: Control-Option-Command-Space) or the menu bar icon to unDock. All removable disks will instantly be ejected. You can also supply your own AppleScripts that will be run when unDock is triggered.