While internal hardware varies, most have an electronic visual display, either backlit LCD or OLED or Hologram. Some use transflective or electronic paper, to consume less power. Most have a rechargeable battery. Peripheral devices may include digital cameras, thermometers, accelerometers, pedometers, heart rate monitors, altimeters, barometers, compasses, GPS receivers, tiny speakers, and SD cards, which are recognized as storage devices by many other kinds of computers.
The top smartwatches that debuted at the 2017 Consumer Electronics Show included the Casio WSD-F20, Misfit Wearables Vapor and the Garmin Fenix 5 series. Apple released on September 22, 2017 their Apple Watch Series 3 model which offers built in LTE cellular connectivity allowing phone calls, messaging and data without relying on a nearby smartphone connection. 
Samsung’s three second-generation smartwatches arrived with real improvements and refinements. At $300, the Gear 2 is the most sophisticated—and expensive—of the trio. The Gear 2 Neo is basically a less expensive version of the Gear 2: It has similar functionality, but it's housed in a plastic body instead of metal and has no built-in camera. And the slimmer Gear Fit is a hybrid smartwatch and activity tracker.
If you don’t need your smartwatch to look business-casual, you want more fitness and exercise features than our top pick, or you’re a Samsung loyalist, the Samsung Gear Sport is a better pick for you. (You can use the Gear Sport with non-Samsung phones, but doing so requires that you install at least four apps.) The Gear Sport handles all the casual notification and message-triage functions of a smartwatch about as well as our top pick—with the exception of voice transcription—but it adds heart-rate monitoring, GPS tracking, swim tracking, and built-in reminders to move throughout the day. It doesn’t do all of these things perfectly, but it does just enough to make for a generally useful smartwatch, with great battery life and a clever interface.
But with a wider choice comes deeper deliberation. What's the difference between a fully digital dial, and a 'smart optimised' analog? What features will actually aid your day-to-day? And which would be totally useless? To answer these questions, and more, we've picked through the best smartwatches on the market to suit your no doubt very busy, hectic and urbane lifestyle.
Built-in GPS and a great workout coach make the Huawei Watch 2 a great companion on long runs and intense workouts. You can leave your phone behind, too, thanks to onboard music storage and the ability to connect Bluetooth headphones to the watch. Like the LG Watch Sport, the Huawei Watch 2 has an LTE version, but unfortunately, Huawei isn't selling that model in the US yet.
When we compared the storage space of the Samsung Gear Sport with the other contenders, it didn’t have the most. With 4 GB — only a quarter of what you’ll get with the Apple Watch Series 3 GPS — you will have to manage your apps so you don’t run out of room. If you like to carry all of your music with you and you have an extensive library, you might run out of space with the Gear Sport.
Speaking of music, that's what really sets this smartwatch apart (especially compared to Garmin's other wearables). The Vivoactive 3 Music has enough internal storage for 500 songs — and they're easy to download to your device using the Garmin Express software. Once your songs are downloaded, you can listen to music without a smartphone. Just connect some Bluetooth headphones to the watch and you're good to go. If streaming is more your game, then you can also download some popular media apps as well.
The Apple Watch Series 4 is now on sale, and it's the best smartwatch you can buy right now. The redesigned device, which starts at $399 for the GPS model and $499 for the cellular version, is the best smartwatch you can buy. It has a larger display and slightly bigger case size while retaining the same rounded square design the watch is known for. Even more importantly, Apple received FDA clearance for a new electrocardiogram feature that can take a 30-second EKG and diagnose atrial fibrillation.