HOW TO: Boot up your Mac from your iPod
Playlist Magazine suggests using an old (or current) iPod as a backup bootable disk for your Mac. To get it going you’ll need to set your iPod to run in disk mode, and then install OS X on it using the original installation disks. If you’re willing to lay out some cash for extra bootable iPod features, pricey software Protogo ($135, yikes!) can boot several versions of OS X from your iPod, as well as add various utilities. How To: Boot up your Mac from your iPod - Lifehacker