Users will be able to press and hold the side button to call 911. The function shares the watch's location and user's basic medical information, including age and existing conditions, with first responders. It also alerts the user's in-case-of-emergency contact.
The app only works if watches are connected to a phone or within range of Wi-Fi.
The new product announcement comes just a day after the deadliest mass shooting in modern U.S. history.
Apple's annual conference, known as WWDC, began with Kevin Lynch, vice president of technology, demonstrating "a dramatic improvement in how it feels to use the Watch."
The company announced other new features for the Apple Watch, including an app that allows users to write notes and a feature allowing users to easily swap watch faces.