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 Gear S3 Frontier: Until we see what Google can pack into a smartwatch with its long-awaited Pixel Watch, the best smartwatch for Android users is the Samsung Gear S3 Frontier. It pretty much has everything a user with an Android phone needs in a smartwatch - GPS, heart rate monitor, water resistance, near field communications, an always-on digital display, messaging alerts and app support. I don’t see a real need to opt for the 3G version yet, which would untether you from your phone completely but adds around $100 to the price. ($549)
Next is the big focus on health and fitness. The Apple Watch can monitor your heart rhythm and suggest you see a doctor if it detects something irregular, it can call the emergency services you've fallen over, and it will keep you healthy by tracking your run. These potentially life saving features are a major reason people are ditching their traditional watches for an Apple Watch.
The company claims that the SpO2 monitor will help its devices look for signs of sleep apnea and other breathing problems, potentially great features for devices that are meant to be worn 24/7. It'll be used primarily in Fitbit's forthcoming Sleep Score Beta, which further analyzes sleep quality using heart rate and breathing data. Starting sometime this November, users with devices that only have heart rate monitors can get a "sleep score" after each night's sleep. Those with an Ionic, Versa, or Charge 3 will presumably have better data thanks to the SpO2 monitor collecting breathing data.
For deeper integration with your Android phone, you can give Google's Wear OS platform a try with Fossil's $275 Q Control touchscreen smartwatch. It lacks GPS and support for NFC payments, which is why the Gear Sport is a better fitness-focused smartwatch for Android users, but Fossil's Google Assistant integration and stylish design make it a solid contender. However, smartwatches with Qualcomm's new Snapdragon Wear 3100 processor start shipping in October, so you may want to hold off until we put them to the test.