Hello,
I find it very convenient to use my iPhone / Android Phone to connect to my Google Account, thanks to the app they have published on their respective stores.
It works the very same way than the SE token for FFXI/FFXIV, meaning it generates a personal 6-digit code every 30 secs. When using it for the first time, the computer client delivers you a unique key to type in the iPhone app, which will thus guaranty the uniqueness of the 6-digit codes displayed on each of the devices you will use.
Here's a screenshot of the app:
The main advantage - non counting the fact you can authenticate from anywhere at anytime, since the app doesn't use any Internet data - is that in case you lose your mobile phone, you can deactivate the app - actually, revoke the codes it will generate - in favor of another one.
Why not adopting such a system in place of the current authenticators, and in the mean time get rid of the limiting factors of the battery and risks of loss/forgetting/breakage. How annoying it is not to be able to play for a month, because you forgot to take the little gadget with you (talking of my own experience), or to be obliged to contact SE when you've run out of battery...
Wouldn't it be a logical evolution of SE's technology?
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Edit 1: The iPhone app IS offline, and it's easy for you to set a password on your phone to prevent intruders to access it. I don't know Android well, but on iOS, there isn't a lot a threats other than the acquaintances who can physically touch your terminal for the moment.
Edit 2: Would use a smartphone people who'd be able/want to. It is out of the question to make the classical tokens that still work useless, or even to stop further production, they still prove they can keep accounts secure.