The biggest and most important features are all related to health and safety. The Apple Watch Series 4 has improved its heart monitoring capabilities from previous models. It can detect unusually high or low heartbeats and, more impressively, it can perform an EKG (electrocardiogram) – which tracks the heart’s electrical activity.

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Apple says the Apple Watch is so accurate at checking for heart rate irregularities that the Watch 4 has been approved by the American Heart Association. Users can export their EKG results in a PDF file that can be easily sent to doctors.

In addition, the Watch’s accelerometer and gyroscope can now detect falls (both slipping and falling). If a fall occurs, the Watch will ask the user if they want to contact emergency services. If there is no response within 60 seconds, the Watch will automatically do so.

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I tested the new Watch for only a few minutes in a controlled environment, so I was not able to test whether the heart rate sensors had been improved or if the fall detection really worked, but I can confirm the hardware improvements are legitimate and welcome.

The Watch Series 4 has larger display sizes (40mm or 44mm) than the Series 3 (38mm or 42mm) without increasing the actual Watch size thanks to the trimming of the bezels. The Watch 4 is also thinner than the Watch 3 and doesn't protrude as much from the wrist.

Inside, the Watch 4 also runs on a newer S4 processor which Apple claims is “twice as fast as the previous model”, though this is unlikely to matter in real-world use: few, if any, users push their smartwatch hard enough to notice the speed difference. I certainly couldn’t detect it during my few minutes wearing the Series 4 and 3 watches side by side.