[evan_]

You don't actually need to have cell service- there's an iPhone app (and presumably apps for other platforms) that lets you just generate new codes at will. You only need internet access to set it up initially, and you can do that with wifi.

won't help you if you have no phone at all but you can generate one-time-use passwords at will, so you could just stock up I guess.

[jackowayed]

Actually, it looks like you can only have 10 active one-time passwords at once.

On the page that lists the current ones and lets you regenerate them it says, "Be sure to throw away any previous versions. Only the latest set of backup verification codes will work."