I don't know the SmartDisk FotoChute 20GB Digital Photo Storage Unit or the SmartDisk FlashTrax units first-hand; but it looks like the FotoChute connects to the camera via USB, so you probably can't take pictures during the download. The FlashTraxx has a Compact Flash slot, you need an adapter for reading other memory cards. It seems a little pricey, too, at $442 from
Amazon; although it says it can do RAW (the reviews on Amazon are, erm, unfavorable for this device).
Here's what I usually do:
-bring a whole bunch of 1 GB cards (my camera uses the Compact Flash type), around ten but at least three. They're small and alot more rugged than any hard drive. If one goes south, I lose at most 60 images or so (less wailing and gnashing of teeth than if I lost images on a larger card)
-bring along a mass storage device with a good-sized hard drive and image preview. I use a Creative ZEN Vision 30GB (the newer model is 60GB and around $350) because it has a CF slot built-in, can preview the JPGs (not Canon CR2 RAW, unfortunately) and store some music and some movies.
-bring a small computer (I use a Toshiba Portege-very light) and copy the files from the ZEN to it, and use it to verify RAW images.
So I fill a card, then move it to the ZEN and let it transfer while using another card in the camera, and keep switching cards during the shoot. At night, make a copy of everything on the computer. (And, if I'm being a pro on this shoot, use it to start catalogging right away.) If I have to move image files off the ZEN, then make a back-up on DVD-R. The general rule-of-thumb here is to never, ever have an image file on only one storage unit for any length of time.
This may be a little too anal for you, but it works for me (and remember: even if you're not paranoid it doesn't mean they aren't out to get you).
HTH.
---Ritch