I contacted Eye-Fi and was told they do not support CHDK and if I install CHDK on one of their card, I would void the warranty.
You should ask him for a complete list of the files that will void your warranty if copied onto the card
edit:
I can understand not
supporting CHDK. It is completely reasonable for them to say, "if it doesn't work, that's your problem, don't bother us". But if eyefi is supposed to work as an SD card, then using it in any SD compliant device should be allowable, regardless of what other software it is running on that device.