To understand why you might want the new cellular Apple Watch, put yourself in the shoes of a wealthy person who drives a weekend car.

In this situation, your iPhone is like your everyday workhorse vehicle, with the muscle to speed through emails, calendar invitations and social media posts. But when it comes time to unwind, you can leave the house with just a cellular Apple Watch — the equivalent of the weekend car — and still have access to a lightweight phone that can handle calls and text messages.

In other words, wearing the Apple Watch Series 3 with cellular connectivity, which Apple will release Friday, is like owning a leisure phone that is excessive but situationally useful. Apple’s first wearable to include cellular may come in handy when you are at the gym and want to leave your phone in the locker, or when you go out for a run and want to remain reachable.

After testing the cellular watch for a week, I found it to be an excellent smart watch that is a significant improvement over the first Apple Watch, which was slow, confusing to use and deeply flawed.

But the cellular version is a luxury that most people probably will not need. The price you pay for those brief moments of respite from your iPhone is steep: at least $399 for the hardware, plus $10 a month for access on your cellphone plan for some carriers. And I seldom found reasons to use the watch without my iPhone to justify the extra cost.

There may also be some early kinks for Apple to work out with the new cellular Watch. Some reviewers discovered that the device occasionally lost its cellular connection, for example. Apple said on Wednesday that the issue was related to the watch inadvertently connecting to open Wi-Fi networks that lacked internet connectivity, and that it was investigating a software fix.

In the end, some people who want a wearable device for things like fitness tracking and a quick glance at mobile notifications will probably be happy with the Series 3 without cellular, which costs $329.

An Overview

Like its predecessors, the Apple Watch Series 3 is a computer worn around the wrist, with a miniature touch screen.

The main difference with the cellular Apple Watch is that some important features, like placing calls, texting and streaming music, will work when you are not near your phone. Credit Jim Wilson/The New York Times

The device requires an iPhone to set up and work properly. Notifications like text messages or social media alerts that come to your iPhone appear on the watch first if you are not actively using the phone. The watch runs apps, including some built-in software for fitness tracking as well as third-party widgets you can download from the App Store.

The main difference with the cellular Apple Watch is that some important features, like placing calls, texting and streaming music, will work when you are not near your phone; the watch shares the same phone number and cellular plan with your iPhone.

To help determine whether the cellular watch is right for you, I abandoned my iPhone to test the watch in a number of common situations. Here’s how that went.

Date Night

Over the weekend, my partner and I made plans to go to dinner at a sushi restaurant. I used the Apple Watch to summon a Lyft car to pick us up at home.

At the sushi bar, I liked that I didn’t have a smartphone constantly buzzing in my pocket, though I got a text that I quickly responded to on the watch using an emoji. My partner and I enjoyed 90 minutes of intimate conversation over omakase with minimal distraction, though I was a bit envious that she could Instagram our gorgeous nigiri.

Verdict: I could have had roughly the same experience with just an iPhone put on Do Not Disturb mode — and a bit of self-discipline.

Dog Walks

For several days, I wore just the watch while walking my dogs. Not having a phone freed up valuable space in my pockets for other items, like my keys, my wallet, dog treats and bags. I liked that the Apple Watch tracked my steps and walking distance to make dog walking feel more like exercise than a chore. I placed a call to my partner with the watch to tell her where to meet me at a park; she said the call sounded crystal clear.

It was also nice that with just the watch, I could still be reachable via phone or text by my colleagues during morning walks — but emails took several minutes to show up after they were sent. It turns out that while texts and calls are done directly on the cellular watch, emails still rely on the iPhone’s pushing emails to the cloud, which then transmits the message to your watch.

Verdict: The watch is good for staying reachable via phone or texts. But in those brief moments when you need to step away from a computer during work hours, a smartphone is still necessary if you rely heavily on email, as I do.

Gym Workouts

I wore the watch and took a pair of AirPods, Apple’s wireless earbuds, to a rock-climbing gym. Again, I left my iPhone behind.

At the gym, I opened the Workout app to track my heart rate and calories burned throughout the workout. During breaks, I used Siri to write a few quick texts to some friends to make plans for the week. I put on the AirPods in the hope of streaming songs on the watch from Apple Music, only to realize that this capability has not yet been released. Apple said music streaming for the cellular watch will come out next month.

Verdict: It was nice being able to stay in touch with people at the gym without a phone bulging in my pocket, but I’d be happy unplugging for a while and tracking my workout with a noncellular Apple Watch. As for whether streaming music makes a cellular watch worth owning, I unfortunately can’t tell you yet.

Grocery Shopping

Here’s where leaving my phone behind and relying only on the watch did not make sense: during grocery shopping. The watch doesn’t have a web browser, let alone a big enough screen, for looking up recipes. But when it came time to check out, I hit the side button to activate Apple Pay and quickly paid for the groceries.

Verdict: A smartphone is a better shopping companion than a watch.

The Bottom Line

The value of the cellular capabilities on the Apple Watch is questionable considering the price you pay each month.

AT&T and Verizon Wireless, for example, charge a network access fee of $10 a month to share your phone plan’s texts, minutes and data with an Apple Watch. That’s about the same as a Spotify subscription, but with the exception of avid joggers and gym rats, people may not use the cellular features frequently enough. Hopefully, over time, Apple will negotiate with carriers to bring the monthly rate down.

Although I think most people can skip buying the cellular model, the Apple Watch Series 3 is the first smart watch I can confidently recommend that people buy. While I don’t personally find it attractive enough to replace my wristwatch, the new Apple Watch is a well-designed, durable and easy-to-use fitness tracker for people who want analytics on their workouts and general health.

Important features like the stopwatch, calendar and Siri work quickly and reliably. And unlike its predecessors, the watch has impressive battery life — on average, I had more than 40 percent battery remaining after a full day of use.

So the final verdict? The Apple Watch Series 3 is the first sign that wearable computers are maturing and may eventually become a staple in consumer electronics.