Battle.net Mobile Authenticator
...Do you play World of Warcraft using a Battle.net account? Protect the account with the Battle.net Mobile Authenticator for your iPhone, an optional tool that offers an additional layer of security to help prevent unauthorized account access. The Battle.net Mobile Authenticator gives you the security of two-factor authentication. Each time you log in to a Battle.net account, you'll use the Battle.net Mobile Authenticator to generate a unique, one-time use password to use in addition to your regular password. Log in with both and you can rest easy knowing that the account is more secure against unauthorized access.