iPhone 5, iPhone 4S, iPhone 4, iPhone 3GS
5 minutes of your time!
A computer, running Windows (XP minimum), Mac OS X (10.5 minimum) or Linux (x86 / x86_64)
An iPhone, iPad or iPod running iOS 6.0 through 6.1 (you may check in Settings / General / About => Version)
A USB cable to connect the device to the computer