Its only drawback is its use of Samsung’s own Tizen OS. Tizen is a custom OS that’s based on Linux. On paper it’s pretty good, letting you pair the Gear S2 with any Android smartphone, not just Samsung Galaxy phones. But it’s nowhere near as developed as Wear OS, which itself isn’t perfect. There aren’t nearly as many apps available as the Wear OS app store, but the core functionality is at least present from what is available.
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. 
If you want the app, notification, and style advantages of an Apple Watch but need better fitness tracking, you can upgrade to the Apple Watch Series 3 and get built-in GPS, as well as waterproofing that allows swim tracking. But the Series 3 costs more than a fitness tracker or even many running watches, and it still has compromises compared with a dedicated fitness tracker, such as a lack of dedicated physical buttons. We think serious athletes are better served by a fitness-specific device.
All but the Martian Notifier claim some degree of water resistance: the LG, Samsung, and Motorola models can survive underwater up to 1 meter for 30 minutes, the Cookoo2 up to 100 meters, and the MetaWatch up to 3ATM, which is equivalent to 30 meters. Only the Martian and Motorola models claim to have scratch-resistant screens (the Martian has an anti-scratch acrylic crystal and the Moto 3 uses Gorilla Glass 3).
The Amazfit Bip is thin and light, looks like an Apple Watch, has a lot of sensors inside—GPS, heart rate, accelerometers, barometer, and compass—and can run for about 30 days (which we confirmed) between charges, all for around $100. Those facts are compelling, but actually using the watch is frustrating, and it doesn’t do any one thing well. The GPS and heart-rate monitors can be slow to start, sometimes drop out, occasionally have wild inaccuracies, and produce results notably different from those of running watches and dedicated fitness bands. The screen is also dim and noticeably low-resolution, and the phone software for managing the watch is dense and unintuitive on Android. (We didn’t test iOS, but the reviews imply that it’s not much different.) The watch materials are plastic and rubber, and look and feel like it. Those are all trade-offs you could reasonably make if you just wanted a Pebble-like smartwatch that tracked steps and showed notifications, but even there, the Bip does not succeed: It often dropped connectivity with my phone (a Pixel 2), and it cannot show emoji—getting a dozen blank squares when someone sends you a thumbs-up sign is not helpful. If all you care about is battery life, the Bip has that, but it lacks useful functions while it’s charged up.
Google confirmed to Tom's Guide that the company won't be releasing its own Wear OS smartwatch this year. The news comes after months of rumors that a Google-branded Pixel Watch running on Qualcomm's latest processor would be launched at Google's October hardware event. Instead, Google plans to focus on adding features to Wear OS on the software side and support the companies who are currently making Android smartwatches. Google's hardware event is Oct. 9.