Chris2J: I would still like a CF Eye-Fi card :-). The fact that this is still not available, indicates that this is technically not possible - however, I do not understand why. Furthermore, I do not understand why nobody has developed an SD-CF adaptor that will facilitate Eye-Fi SD card usage, so you do not have to butcher the adaptor to not block the WiFi signal - even an adaptor that will somehow boost WiFi transmission. The WiFi solution offered by Nikon is just too expensive.
I have an 'Extreme CF Adapter' with a Transcend wifi card, works alright in my 400D, as the original review said, they're a bit clunky to use but fro casual use it's fine