If you press your iPhone’s power button 5 times in rapid succession (don’t try it until you finish reading this post), your iPhone will place an emergency call, presumably to 911 in the US.

Once you start the process, you’ll hear a loud alert siren and see a countdown appear, giving you an opportunity to cancel the call. To cancel the call, you’ll need to press the Stop button, then press the Stop Calling button that appears.

Here’s what this looks like on my phone:

Not sure how long this feature has been in place, but I thought it was worth sharing.