At their September event, Apple spoke of their annual upgrades to their iPhone and Apple Watch lines. While the iPhone update was mostly limited to the processor and camera, the Apple Watch had some more significant improvements, notably including the capability to capture an electrocardiogram, atril fibrillation detection, fall detection, and an emergency SOS feature.

While the original pitch for the Apple Watch included health features, it was more concerned with being a workout accessory and general activity tracker. Over the years, it has grown more sophisticated at being not just an accessory, but a true guardian of the wearer’s health. Features like ResearchKit are making it possible for medical research to be conducted on people on a daily basis. It’s clear Apple is going to continue moving the Apple Watch in this direction.

This has potential to be transformative to public health, but there’s a problem: this device is limited to people who have iPhones, which makes up about 2 in 5 US phones and 1 in 5 phones worldwide. That means these features are not available to the vast majority of smartphone users, a market that is currently starved for a comparable product. And while there are finally some signs of life for an alternate smartwatch platform, Apple’s actively working with the FDA on some of their features; they’re simply better positioned to have accurate results.

When the iPhone launched, it was tethered to a computer running iTunes, but with its fifth release, the iPhone went PC-free and became fully self-sufficient. While it’s unlikely that the Apple Watch could ever be completely run without a connection to some other device, surely there will be many features that aren’t dependent on an iPhone. The health care features alone would be transformative for many people; there are absolutely people who would buy an Apple Watch just to have a modern health guardian device. Are they obligated to make the Watch work without the iPhone? Of course not. But it would dramatically expand the market for the device, and provide a marked improvement to the health and lives of people who can’t get one today.

The Apple Watch is a unique product for Apple Retail. The retail operation is designed today to showcase a few demo models of a product, sitting on a table, chained to a desk. Guests can get a very good feel of how a laptop or a phone works by touching it while tethered. You can play with the iPhone’s software or check Facebook on a MacBook Air and reasonably intuit how this thing will fit into your life. Apple has perfected that purchasing experience over the last decade because their products have fundamentally all been disconnected from the user.

While the Apple Watch shares some similarities to Apple’s other mobile products, the experience of using one is totally different. A smartwatch becomes an augmentation, an extension of your body. It has to fit your wrist, and be comfortable, and provide subtle utility. It must look and feel good to the person wearing it. A watch is often more about fashion than utility.

Proving those elements will be what convinces someone who walks into an Apple Store to walk out with an Apple Watch. So to really try an Apple Watch before you buy one, you’re going to have to wear it.