In the future, iPhone users could set off a "panic mode" by unlocking their phone with a specific finger.
The potential feature was detailed in a patent filed by Apple last year and published by the U.S. Patent and Trademark Office on Thursday.
There is no guarantee that Apple will ever include a panic mode in any of its future devices; technology companies file a lot of patents that never make it to market.
NBC News reached out to Apple to ask how or if the company was planning to implement the feature, but Apple did not respond.
But it's easy to see how this technology could be useful. Right now, Apple's Touch ID sensors can read multiple fingerprints to unlock an iPhone or iPad, and there is no reason that iOS couldn't assign different functions to a thumbprint versus a pointer finger.
The patent proposes a panic mode that would alert friends and family that the user could be in danger, as well as possibly flash a light and emit "a noise similar to that produced by a car alarm" to deter criminals.
Apple also proposed a private mode for non-emergency situations that would let people unlock their phones but restrict access to sensitive information, such as text messages and emails, while out at a busy bar or restaurant where it might get stolen.