I bought the first generation Apple Watch (colloquially known as the “Series 0”) when it came out. Doing so was a measured leap of faith; it wasn’t entirely clear to me at the time what the Watch was for. Most of its features were things I could already do with my iPhone, albeit a bit less conveniently. Track my runs? Check. Show notifications? Check. Play music? Check. Tell the time? Check. Then there was the inconvenience of having another device to charge and the expense of periodic hardware upgrades.

Still, as a digital designer and strategist, it’s important for me to be up to date on form factors and technologies. I also trust Apple. So I bought the watch and went all in, using it daily to track my activity. Although I’ve grown to really like the Apple Watch, I haven’t seen it as an essential part of my everyday carry kit like the iPhone is. I can easily make it through a day without my watch, which is not something I can readily say about my phone.

To Apple’s credit, they’ve improved the product tremendously over the past three years. (Sometimes by making major changes to fundamental interactions in its operating system, which was somewhat awkward at launch.) Even though it’s rather slow now, and its battery doesn’t last as long as it used to, my Watch is better today than when I bought it. (A notable example: I use it dozens of times every day to automatically log into my Mac, a time saver.) Apple has also released subsequent iterations of the hardware that have added significant improvements such as GPS tracking and a cell radio. Still, I’ve resisted the impulse to upgrade. The Watch is not an inexpensive purchase (I prefer the stainless steel models), and as said above, I haven’t thought of it as indispensable.

That changed yesterday when Apple announced the Series 4 iteration of the Watch. Apple’s COO Jeff Williams introduced the product by emphasizing that it’s meant to serve communication, fitness, and health roles. For most people, a smartphone can fill the first two of those roles. The third, however, can be much better served by a device that is in constant contact with the body, like the Watch.

That’s what Apple is focusing on. The Series 4 Apple Watch introduces various health-related features that are likely to improve many people’s lives in significant ways. The first is fall detection: Apple has studied the patterns of movement a person’s wrist follows when he or she falls, either by slipping or tripping. When the new watch detects a motion that it thinks may be a fall, it offers an affordance to dial emergency services. If the body is unresponsive after sixty seconds of having shown the notification, then the Watch dials emergency services automatically. This seems like a boon for older adults who are at higher risk of serious injury from falls.

Other health-related features allow users to monitor their circulatory rhythms for anomalies. The current (until next week) version of the watchOS offers the ability for the watch to show alerts for elevated heart rates. (Alas, I’ve turned this feature off to conserve battery life on my older Watch.) The new Watch improves on these notifications in various ways: it can now show alerts for unusually low heart rates or irregular heart rhythms.

More importantly, the new Watch allows users to take ECG (electrocardiogram) readings on their wrist and share them with their physician. The Series 4 Apple Watch is the first device available over the counter that offers this feature, and it’s been granted a De Novo classification by the U.S. FDA. For people with heart conditions (which fortunately I’m not), this could be a game-changer. (I expect the Watch’s readings won’t be as precise as those provided by professional monitoring systems, but even a little information is better than none​ when it comes to potentially life-threatening health conditions.)

The old 1960s Star Trek TV series featured a device called a tricorder. It was packed with sensors, and characters on the show could use to take readings of their current surroundings and beings in it — including diagnosing medical conditions. While the Apple Watch’s purpose wasn’t clear to me when I first bought it, it is now: It’s a smart, personal tricorder. I expect it’ll gain more sensors over the years, and those sensors and the data they collect will make it possible for you and I to lead longer, healthier lives. It represents a democratization of technologies that could have a ​measurable positive impact in the world. As a middle-aged man, this gives me hope; I’ll be upgrading mine for the first time (but not the last) this year.