One of the biggest complaints of smartwatches is that they're really just dependent accessories to your phone. They need a phone to work.

Not all of them, though. The Samsung Gear S2 3G is a smartwatch that has its own cell service. It can work without any phone at all. I wore the Gear S2 3G for a few weeks. And, now I've taken it off. It's an amazing little demonstration that a watch can be its own phone...but I can't see enough reasons for most people to buy this.

It's a phone

I took the watch off its charger and slipped it on my wrist. No phone in my pocket. With this watch, you don't need a phone: it's got a little e-SIM inside. The Gear S2 3G makes phone calls. It also gets messages, texts and checks the weather while using a 3G network or Wi-Fi to connect.

It's a nice-looking watch: it looks almost exactly the same as the slick Gear S2 I loved last year. And it's basically the same smartwatch...with extras. You're getting a bonus speakerphone element (which, like an Apple Watch or older Samsung Gear watches, also works when paired to your phone) along with built-in GPS. But it's also really thick. It felt OK on my wrist, but anyone who prefers smaller watches or bands might object.

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Even though it will make calls on its own, this watch first needs to pair with a Samsung or Android phone to get started (iPhone support is said to be coming later in 2016, but Samsung hasn't confirmed whether that will include support for the 3G version's speakerphone calls). Once it's set up with a data plan from an AT&T, T-Mobile or Verizon account, you can turn that other phone off and just use this watch. The AT&T version can share your phone's number via NumberSync, while the Verizon and T-Mobile versions get a separate phone number that can get forwarded calls; each will also end up costing about $5 extra per month on your wireless bill in the US in order to share data on a plan that allows it. I tested an AT&T version.

My wife could hear my calls just fine outside: the microphone's great. But the speaker sounds weak. You can pair a Bluetooth headset and use that instead. Pairing a Bluetooth headset also means you can use the watch to store music or even stream music, turning it into a little self-contained wrist entertainment system.

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It connects to messages, apps and navigation

Again, Samsung's Gear S2 watches run Tizen, a separate operating system with a separate app store from smartwatches on the Android Wear platform. There's nothing really wrong with that, but it does mean that the Gear S2's on its own app island, with fewer choices of what to install. And it also means that for some features like navigation or email, you have to make sure you install or set up the Samsung Gear-ready apps and conduits that work with it (unlike Android Wear or Apple Watch, which knits into phones a little more seamlessly).

I was able to check messages, look at news, check the weather, find restaurants with Yelp, navigate on my wrist and get directions, while even using the on-board GPS to track and map runs as well as walks with Samsung's S-Health fitness app.

I can't say I did all these things frequently, though. I don't power-use watch apps, mainly using my smartwatch for basic information. To access more, then I go to my phone. See, that's the thing: I always have my phone on me. Why would I ever leave home without it? There's no way I'd rely on my watch as a phone.

And, that, ultimately, is the problem with the Gear S2 -- and maybe the whole idea of a standalone "watch phone."

Samsung's wrist-based version of Samsung Pay is coming to all Samsung Gear S2 watches - even the non-3G ones -- later this year, but it'll only work when paired with a Samsung phone.

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I've been down this road before

There was another stand-alone 3G-enabled Samsung watch: the Samsung Gear S. It didn't make much of an impression on me. Its apps were weird, and it was hard to use.

Samsung's much better Gear S2 -- the original Wi-Fi and Bluetooth model that was released in late 2015 -- doesn't make stand-alone phone calls, and doesn't even have a speaker for Bluetooth speakerphone calls like older Gear watches did. But the S2 3G version does. And that might matter to some people.