A friend of mine drop in may hand one this card from Sandisk (see image), that is the same as Eye-Fi in USA (http://www.eye-fi.com).
I soon plugged the card in the FEZ-Hydra SD slot (after a bit of config on the PC). I made very stupid C# function that create a fake JPG mimiking the dir struct of a camera memory, and as soon as i close the write strem, the image has flight via wifi to my PC (using eye-fi control center).
It seems that this card recognize only few photo file type (jpg) and few video type (not tested).
The interesting part is that this card is based on Atheros MCU running eCos (GPL and free) and complite source code is downloadable from Eye-Fi site (http://support.eye.fi/cards/specs/ecos-open-source-license/).
I didn’t dig deeply in the stuff, but I think that is an interesting solution for big datalogging, security image shooting and so on when plugged in the FEZ boards.
There is anybody that have done some work on this kind of cards ?
PS: This card is not really perfect, but may be firmware can get better …