In order to be able to use a smartwatch, you need to have a smartphone. While some new smartwatches can work on their own as a standalone smartwatch, you won’t be able to benefit from all features without a smartphone. You also need to download the accompanying app on your smartphone and turn on the Bluetooth to connect your smartphone with your smartwatch. So the model of your smartphone also plays a role when you are comparing different smartwatches. Some smartwatches are hybrid meaning they can work cross platforms (iOs & Android). However, some like iWatch (Apple) really works only when paired with the iPhone (Apple). Once the devices are successfully paired (connected) you start receiving notifications from your phone to the smartwatch and can control some of your phone’s features like music from your smartwatch.