The fingerprint scanner for the iPhone 5S is more than just a high tech way to unlock your phone. It's also poised to do other things.
Called Touch ID capacitive sensor, it is sensitive enough that you only need to tap your finger on the home button. The sensor maps the ridges in your fingerprint, and it encrypts and stores your fingerprint data on the A7 Chip. It won't be going anywhere else. Not to the iCloud, or to any Apple servers.
The extra security measures are necessary since your fingerprint data will be linked to your iTunes account. Every time you make a purchase, just tap the home button.
You won't notice the fingerprint scanner on the home button, because they've managed to add the sensor in to the button very smoothly. The laser cut sapphire crystal surrounded by a stainless steel detection ring sits below with a tactile switch behind it.
The only problem here is what if it gets spoiled from double tapping the home button to close apps? Where do you replace this? How would it affect the security?
FastCoDesign makes an interesting argument that with the new fingerprint sensor, Apple is making you the device. It's worth
a read. Check it out.