Apple released iOS 7 beta 4 earlier today with a number of performance improvements and minor UI tweaks, but an internal code reference points to a big upcoming change — the addition of a fingerprint sensor in a future iPhone.
Specifically, the references suggest that the fingerprint sensor would be a part of the next iPhone’s home button. Here are the relevant strings:
“Photo of a person holding an iPhone with their right hand while touching the home button with their thumb”
“A fingerprint that changes colour during the setup process”
“Recognition is complete”
The strings are a part of a bundle named “BiometricKitUI,” and are what iOS would read to the user if VoiceOver is enabled. 9to5Mac’s sources say that the UI part of the fingerprint scanning system has been done, and that the feature is focused on unlocking the iPhone.