I just don't see the point!
"Consider the following scenario: You have a carefully prepared PowerPoint presentation plus a spreadsheet of key ROI numbers to impress a prospective customer on your laptop and, as a security, you have backed up these key files (say on a memory stick). Then, just as you arrive, you accidentally bump into some furniture and knock the laptop. Guess what? You find you can't boot it up let alone access the hard disk (Laptops are susceptible to getting knocked a lot, and the disk drive is often affected). Then you are stymied because your backed-up files cannot be restored, let alone run."
But the "solution" being advertised here doesn't help with this situation!
Having the files backed up on an external USB hard drive is no more useful that having them backed up on an external USB flash drive.
If a machine is available at the customer's site that has the appropriate applications installed (in this example MS Office, so that's about 99.9% of all business PCs) then either backup device just needs to be plugged in to that PC to be up and running.
If the customer does not have a copy of the application available (non-standard application?) then sure you can get your screwdriver out and start fiddling with rebuilding your laptop in front of this prospective client - but I don't think that would impress greatly. There must be a better solution than this!
Maybe companies that do demonstrations or presentations at client sites that require applications that will not be available at those sites, can't run from a flash drive or standard USB hard drive, can't run from a CD-ROM or DVD-ROM or be installed quickly to a borrowed PC, and where the presentation is going to be given by a single person or a team that all share one laptop and that computer is delicate enough that the hard drive has a high probability of failing, yet the screen, keyboard, battery PSU etc. can be 100% relied upon, and the customer is not understanding enough to reschedule if there is a problem (but can sit thumb-twiddling for 20 minutes while an un-trained salesperson performs a hard-drive transplant)... then it may be worth it.