Here's how the Eye-Fi card and service work, at least in the way that I have them set up. This differs for the Eye-Fi "Home" card, or if you don't have the "upload to Internet" (or whatever it is really called) enabled.
- You take a picture, and dump it on your card
- Your card notices the picture gets on the network and looks for your PC. If it can't find your PC, it uploads directly to api.eye.fi (an Eye-Fi managed server on the internet)
- If it can find your PC running the Eye-Fi Manager, it uploads to your PC and lets the PC upload to Eye-Fi. The PC keeps a copy if you asked it to.
- The Eye-Fi server looks at your preferences and uploads pictures to Picasa, Flickr or whatever you want.
There were a few people working on a server to replace the Eye-Fi Manager. I have not heard about that effort in a while. There are some security mechisms built into the card to keep it from uploading to unauthorized software which make this hard to do. I don't think this is Eye-Fi being nasty or hating Linux or anything. It's a genuine security feature to keep the "bad guys" from tricking your card into sending all its pictures to the evil hackers. I would love to write a open replacement for this part of the Eye-Fi Manager, but I'm not sure how feasible that would be and still ensure that the "bad guys" don't do the same. I'd be more than willing to give it a shot if I had some idea how the card authentication worked.
What I do personally is that I trust Eye-Fi with my pictures. I let them go to Eye-Fi, then get uploaded to Picasa. I paid the $20/year or whatever it was to get 10GB of extra storage at Google. Then, I use the official Picasa API and some perl to download the pictures from Picasa back to my web server where I stick them in my own photo album. The downside to this is that I have to trust Google and Eye-Fi with my pictures along the way. The upside is that when I take a picture, it automatically gets backed up in three different places.