It seems that the iPhone 5S' Touch ID sensor works with far more than just fingerprints. We've seen the iPhone 5S locked and unlocked with cat's paws, and now a video apparently shows a guy locking and unlocking the device with his nipples.
In the genuine-looking video, published by Japanese site Rocket News, we see a male person successfully going through the process of registering "fingerprints" through the Touch ID sensor with his right nipple. Then, he proceeds to unlock the phone with it, and it works in less then a second.
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A second person then tries to do the same with his (unregistered) nipple, but the phone won't unlock.
In a separate video by Rocket News (below), we see a person locking and unlocking the iPhone 5S with his toe, and then unsuccessfully trying the same stunt with his nose.

It's a pretty awkward way to lock and unlock your iPhone 5S, but it does pose the inevitable question: if you can unlock the device with your fingers, toes, cat's paws and nipples, which other weird body parts can be used? We're sure we'll find the answer to that enigma soon enough.
Image: Rocket News/YouTube