The standard Canon support for the Eyefi card is limited to telling you the card's status (connecting, uploading, disconnected) and the upload status of the pictures.
If you want to register on a wireless network you need a PC and the Eyefi's software (or a replacement: Dave wrote a config command line utility in C, I wrote another in C#).
My implementation permits you to list the wireless networks (SSIDs) visible from the Eyefi's, and specify a password for connecting.
It allows also to list the networks configured on the card in order to delete any of them.
More functionalities could be added, but this two are what you really need when you're on the road