http://www.macnn.com/articles/13/03/21/sends.codes.to.findy.my.iphone.sms.numbers/
Apple enables two-step verification option for Apple IDs
updated 04:37 pm EDT, Thu March 21, 2013
Sends codes to Findy My iPhone, SMS numbers
A two-step verification process is now an option for Apple ID accounts, reports say. The option can be accessed on Apple's website, and once enabled requires entering a PIN before making an account change or a purchase on iTunes or the App Store. Codes are sent via Find My iPhone or a text message.
When getting a code on an iOS device, a lockscreen message tells users to "unlock to view your verification code." In case a device tied to an Apple ID ends up lost or stolen, a special recovery key can be used.
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Removing (no longer) "trusted device"
The partial reliance of the new 2-step verification process on "trusted devices" raises the issue of removing a device if you've sold it, for example. A FAQ ostensibly addresses this issue:
"What if I lose or give away one of my trusted devices?
If you no longer have access to one of your devices, go to My Apple ID to remove that device from your list of trusted devices as soon as possible so that it can no longer be used to help verify your identity."
But there appears to be no way to remove a device from the list of trusted devices UNTIL that device has been verified, and if you no longer own it (and it has been wiped), you can never verify it.
Any suggestions? --Thanks.