【Complete Series Archives】

Apple's new health features represent a transformative change for the Apple Watch.

The Complete Series Archivessmartwatch that was once marketed as a fashion-forward (lol) tech gadget with a smattering of health and fitness features is now creeping closer and closer to a full-fledged medical device.

Never has that been more clear than during Wednesday's press event, when Apple unveiled the Apple Watch Series 4, its most health-centric wearable yet. In addition to the fitness features that Apple's been steadily improving for years, the heart rate sensor on the Series 4 is capable of taking an electrocardiogram (ECG), a test that can diagnose serious heart conditions, like arterial fibrillation (AFib).

When the ECG feature becomes available later this year in the U.S. (no word on international availability yet), the watch will be able to detect AFib and lowered heart rate, according to Apple. The company has received some FDA approval on the ECG test, and the head of the American Heart Association made an appearance onstage to endorse the device. Outside of heart health, the company also added a new fall-detection feature.

Besides laying bare Apple's ambitions in the healthcare arena, it's difficult to overstate how significant these features are for Apple.

As my colleague Chris Taylor pointed out in Mashable's live coverage of Apple's event, heart disease is the number one killer in the United States. Letting anyone access an ECG at the tap of a button (or digital crown, in this case) could have huge implications for detecting and treating heart disease. And while some cardiologists were quick to caution that more data is needed in order to evaluate the Apple Watch's effectiveness, the prevalence of heart disease in this country alone means there's a massive need for consumer-ready heart tracking data.

This Tweet is currently unavailable. It might be loading or has been removed.

It's also a brilliant business move for Apple. By adding sophisticated heart-monitoring features and fall detection, Apple is making a compelling case for why older people, a group not typically thought of as early adopters, should consider an Apple Watch.

This Tweet is currently unavailable. It might be loading or has been removed.

Insurance companies are likely to take notice, as well. Some insurance companies already subsidize Apple Watches just for the fitness benefits. Now that ECGs are in the mix, though, it's not difficult to imagine that an Apple Watch could one day be prescribed, just as other medical devices are.

This Tweet is currently unavailable. It might be loading or has been removed.

We're likely still a ways out from that happening, even if it's the direction Apple eventually wants to move toward. And in the meantime, there are some potential drawbacks to Apple's big pivot to health.

Inaccurate readings could prompt unwarranted health scares, which could result in costly emergency room visits or unnecessary trips to the doctor. And handing over your Apple Watch data to your physician has potentially significant implications for privacy, though the company already dabbles in medical records.

If Apple is able to persuade physicians and healthcare providers to also buy in to its tech, though, then it could easily turn the Apple Watch into one of the company's most important products.

No matter how many times CEO Tim Cook calls the Apple Watch the best-selling smartwatch, there's a reason the company has yet to break out sales figures on the four-year-old product: the company simply hasn't sold enough.

Compared with smartphones, smartwatches are still a relatively new category, and no company -- Apple included -- has been able to effectively make the case that the wearables are the must-have gadget in the same way a phone is. But by putting health first, Apple may actually have a decent shot at changing that perception.