Yikes... for the price it seems like you might as well get a cheap netbook with a harddrive, which you can at least use for other things like web access or taking notes. Personally, I'd just get more memory cards as needed. Those ones you listed are cool devices and all, just too expensive for what you're getting.
>>They're not fragile enough to justify a photo storage hard disk purchase, are they? What do you guys think?<<
It's important not to put all your eggs in one basket. I'd recommend backing up to an external hard drive (an ioSafe would be a great choice: www.iosafe.com/3) and backing up online using a service such as Mozy. Doing it that way, your data will be protected against pretty much every eventuality ... flood, fire, device failure, coffee spills, cats, etc., etc., etc.
If traveling overseas I'd certainly lug around my 12.1" ultraportable (netbook just ain't my thing). But if it's just a 1week trip or day shot session I've got a two 16GB and three 8GB to keep me happy pumping out ~12MB/RAW onto them.
At the end I throw them onto my hardware RAID5 array for archival when I get back home.