Does anyone know where I can purchase the TechTool Protege?
far more cost effective solution AND you can install DiskWarrior and DataRescue and Drive Genius on it as well for a very good utility drive and much easier to maintain and update for booting different macsTechTool also offer something called Protogo, it's a little less, same tools as Protege but you use your own external firewire drive/flash drive. More info at Micromat - Protogo
Also, if you have a portable firewire HD, you could install an OS on it and some your favourite utilities and it would about the same price as purchasing this keychain, I think.
I would recommend Disk Warrior as a must have and Data Rescue and perhaps Drive Genius or TechTool but the software alone would be $300 or so. You would then be fully armed for almost any potential issue at about the same cost as the keychain.