I didn't know about the HP ones, but i do remember the Casio watches (always thought they were ugly, lol).
But i do feel this is different.
I did bought myself a 64Mb memory stick and find it really usefull.
Most of the times i use it to deliver downloaded patches and/or upgrades at work.
But i also use it for friends, and even one friend on a pc, it works great.
The only thing is.... it's just a little stick and i'm always worried of loosing it.
I know some are capable of being chained to your keychain, but this one isn't (maybe i should have looked for those ones).
Soooo, i think a watch, mixed with a memory module can be pretty usefull