Take the new fall detection feature as a prime example -- it's all about safety. Should you fall while wearing the Apple Watch Series 4, the watch will sound an alarm, tap your wrist and ask you if you're alright.
If the watch doesn't detect movement for "about a minute" after the fall, a 15-second countdown begins before it eventually calls emergency services, along with alerting your emergency contacts that you've fallen and are no longer moving.
If you'd like to enable fall detection, open the Watch app on your iPhone ($1,000 at Amazon) then tap Emergency SOS. Slide the switch next to Fall Detection to the On position. For users aged 65 or older who have entered their age during watch setup, or in the Health app, fall detection is automatically enabled.
Apple states it is possible to accidentally trigger fall detection if you're highly active, particularly in high-impact activities. So if you find yourself accidentally triggering fall detection, repeat the steps above to disable it.