Yesterday, Apple announced that the US Food and Drug Administration cleared two new features for the Apple Watch Series 4. One is an advanced method of monitoring the heart called an electrocardiogram (EKG), and the other is the Watch’s ability to detect and notify the user of an irregular heart rhythm. Both features will be available on the device later in 2018 (not at launch). The news sounds exciting, but there are some important caveats that limit how useful the new gadget will be.

First, the FDA clearance letters for both the EKG and irregular rhythm notification functions note that they are not intended to be used by people under the age of 22. The irregular rhythm feature is not intended for people who have previously been diagnosed with atrial fibrillation, which is one of the most common causes of an irregular rhythm. (In other words, this feature is best used by people who are already well.) And both letters specify that the apps are “not intended to replace traditional methods of diagnosis or treatment.” They might provide extra information and that information might be helpful, but they won’t replace a doctor’s visit.

the FDA approved the two new features only about a month after the application was first submitted

Second, it’s important to understand that the FDA has “cleared” both apps, but that’s not the same as “approving” them. There are usually three ways to get the FDA involved in a new project, according to Jon Speer, co-founder of Greenlight Guru, a company that makes quality management software for medical device companies. The most advanced is FDA approval, which is done only for Class III products, or technologies that might have higher risk but also a higher benefit. (Think: implantable pacemakers.) Approval is the gold standard, and companies need to do a lot of testing to receive this designation.

The Apple Watch is in Class II. For Class II and Class I, the FDA doesn’t give “approval,” it just gives clearance. Class I and Class II products are lower-risk products — as Speer puts it, a classic Class I example is something like a tongue depressor — and it’s much easier to get clearance than approval.

Most of the time, products are cleared because they’re sufficiently similar to an existing medical device that the FDA already regulated. Apple, however, has emphasized that it has received a “de novo” classification for the EKG feature. That means that, although it’s still in Class II in terms of risk and hasn’t gone through as much testing as an “approved” device, it’s unlike anything else on the market. It is the first direct-to-consumer EKG wearable. (Last year, the FDA approved the AliveCor KardiaBand, a watch accessory that essentially does the same thing, but that wasn’t direct-to-consumer.)

Historically, claiming something is “de novo” is a less common way of getting devices to market, but it’s becoming more popular, adds Speer, as we blend fitness gadgets with emerging technology. “We’re going to continue to see these wearable technologies cross over and become regulated as medical devices,” says Speer. “Think about things that are indicators of your health: blood pressure, heart pressure, respiratory rate, maybe things like diabetes management. The possibilities seem endless.”

As just one example, Omron has been working on a blood pressure monitor that looks like a smartwatch. Last year, the European Union announced that the Natural Cycles fertility-tracking app can be classified as a medical device. (This may not have been a wise decision, given the controversy around the app.)

“There was a point in time when the perception was that technology companies were not interested in health care and not ready to ball play,” says Linda Pissott Reig, co-chair of the FDA section of law firm Buchanan, Ingersoll & Rooney. Now, we have Apple embracing the health care arena and this high-profile announcement, and the FDA is more open to approving these new technologies. Reig points out that the FDA approved the two new features only about a month after the application was first submitted. “The fact that they’ve had this success in short order with the FDA responding to their application is going to encourage others to follow in their path and to also be encouraged that these opportunities that the FDA will embrace and bless and allow to proceed,” she says.