Watching your back

Apple has been trying to make the Watch a first-class fitness tracker for years. What's really new -- and to some, slightly unnerving -- is Apple's focus on turning the Watch into a wearable guardian.

Let's say you're out for a stroll when you stumble over your own feet. (This is, sadly, not unusual for me.) If you have the Series 4's fall detection feature enabled, the Watch will spring into action and ask if you're all right. In the event you don't respond for a full minute (complete with obnoxious alarm sound) the Watch contacts emergency services and pings your preset emergency contacts.

I have no shame so I've thrown myself around this office more times than I care to admit in the hopes of triggering that fall detection. No dice -- the Watch is looking for specific changes in wrist motion and acceleration before it raises a flag, and it's sophisticated enough that false-positives are very hard to come by. As thoughtful as this feature sounds, though, it can only help you if you've specifically turned fall-detection on. The exception to this rule is if you're 65 or older, in which case the feature is enabled by default.

Having the feature on doesn't noticeably affect the Watch's battery life and it's difficult to trigger accidentally, so really, there's no reason not to enable it on day one. That said, the feature's benefits are crystal clear for older people and their caretakers -- even short falls can severely injure the elderly, and if they happen to be wearing an Apple Watch, it basically acts like an ML-powered LifeAlert pendant.

As of this year, the Apple Watch now also pays closer attention to your heart. Heart-rate monitoring has been a key feature since the beginning, but now the Watch is set to warn you when your BPM is too high or low while you're at rest. (These thresholds can differ between people so you can set your own range inside the Watch app on your phone.) Thankfully, my heart tends to hang out at around 60 to 65 beats per minute, so I haven't had to deal with one of these chilling warnings. Hopefully, you won't either.

As a heart-rate monitor, the Series 4's best days are yet to come. Despite all of Apple's big talk about the turning the Watch into a wearable ECG machine, you won't be able to use the Series 4 as one until Apple activates the feature later this year. Same goes for the Watch's ability to detect and flag irregular heart rhythms. Both of these features were cleared by the FDA just one day before they were announced on-stage in Cupertino -- a significant milestone. Clearances aside, just keep in mind that neither of these smart heart features is meant to completely replace traditional diagnoses; it's best to think of them as early warning systems. I'll revisit this review when these features go live, but for now, you'll just have to listen to your heart yourself.

Battery life

Apple says both versions of the Series 4 are rated for about 18 hours of use, but -- as usual -- that's a pretty significant low-ball. I've been able to wear the Apple Watch for between 24 and 36 hours before needing a recharge. Obviously, that's going to change depending on what you use the Watch for, but even after full days of fairly consistent tapping and prodding, I could still go to bed knowing the Series 4 would wake me up in the morning.

If you're very careful to use the Watch sparingly, you could get it to hit a full 48 hours. That takes work, though, and if you drop the Watch onto its magnetic charger for about half an hour once a day, you shouldn't ever have to worry about longevity. That said, it wasn't that long ago that I tested a premium smartwatch with nearly four days of battery life, so it wouldn't be fair to say the Series 4's battery is best in class.