Unfortunately it requires some special characteristics in the board schematic, to not risk destroying the chipset.
"Warning: please do not try to use SF100 directly on the application system if the scenario is not in the above two cases."
..from their manual. I agree with them, it could be dangerous to drive the SPI chip while it's connected if you don't know exactly how it is connected and that it really is safe on that particular board..
The only thing that is required is that they can safely pull the HOLD# pin to ground. Any sane design will have a pull-up resistor on that line (and most other SPI lines, for that matter). That said, there probably _are_ boards that do not have a sane design. Such a shame.
[Oh, it obviously also doesn't work if the chipset or the motherboard design uses HOLD# for something else already. This isn't commonly done though].
Aaaaaanyway... It is really simple to build a device like this yourself for a few bucks. SPI flash has many nice characteristics.
Segher