With watchOS 5, Apple Watch intermittently analyzes heart rhythms in the background and sends a notification if an irregular heart rhythm such as AFib is detected.3 It can also alert the user if the heart rate exceeds or falls below a specified threshold.

Fall detection utilizes a next-generation accelerometer and gyroscope, which measures up to 32 g-forces, along with custom algorithms to identify when hard falls occur. By analyzing wrist trajectory and impact acceleration, Apple Watch sends the user an alert after a fall, which can be dismissed or used to initiate a call to emergency services. If Apple Watch senses immobility for 60 seconds after the notification, it will automatically call emergency services and send a message along with location to emergency contacts.