Is this a 'good idea' or is there something wrong with it.

1) Install a live linux distroto an Expresscard flash drive.
2) Use it in my laptop when needed as the 'permanent' linux install
3) If using another machine (either laptop or desktop) plug the express card into its USB adaptor and as long as the PC can boot USB device then I can use it there as well.

I have never used a USB live before on a flash drive but I am guessing since the flash drive is RW a live install is more like a proper linux install than a read only CD/DVD.