The new Eye-fi Pro 4gb cards are faster, handle raw format, and allow an adhoc connection. Cost more too, about $150
I still have an "Eye-fi Explore 2gb" and I really like it, but it doesn't do adhoc, only infrastructure. To add new wifi networks to the card you need to plug the card into an SD card reader in a usb port of a PC running the eyefi manager software. This means you need to plan ahead if going out with only the camera and not your PC. Captive portals won't work either, as there's no interaction between card and hotspot other than SSID/password. I have mine configured with about a dozen known SSIDs as well as alot of router default name/password combinations. Also, it comes with a year long subscription to the AT&T/Wayport network (mcdonalds, starbucks, etc)
It does a reasonably good job (in urban areas) of geotagging by looking at SSIDs in the area when a pic is taken ("fake GPS" similar to Loki or Google Latitude) This is with any
SSIDs, not just configured ones... when the pic is taken it tags it with SSIDs it sees, and if it can't upload then, it will later upload with that data and consult the database to attempt to locate where the shot was taken.
I've got an old point and shoot Canon running CHDK. I can turn on the intervalometer or motion-detect setting, set the camera down somewhere, and if it's in a wifi hotspot that the card is configured to, I'll see the resulting pics on any internet connection by going to picasa or flickr, etc. Not exactly a streaming motion detect spy camera but it's fun.
Here are some collected links if anyone's interested:
CHDK (Canon Hackers Development Kit) If you have a Canon camera and don't know about this you should really check it out:
Linux Eye-fi config tool:
Jeff Tschang's Standalone Eye-fi server: