updated 09:30 am EDT, Tue September 10, 2013
Leak consistent with other rumors
A leaked photo of an iPhone 5S manual appears to point out the device's reported fingerprint sensor, merged with the Home button. Significantly the technology is identified for the first time as the "Touch ID" sensor, and accompanied by an expected gray ring. The image doesn't, however, explain how Touch ID will work.
It's typically believed that the sensor will let people unlock an iPhone by holding down a finger or thumb for a few seconds. It could in theory allow multiple user accounts in iOS 7, but there hasn't been any evidence of that feature in betas. Instead, it currently appears that the sensor will serve simply as a faster, more secure way of unlocking a device.