The accessory is synchronized with phones on various OS: Android, iOS, etc. The characteristics of the gadget necessarily contain a mention of compatibility with one or more OS. For example, in the parameters of Watch GT Black, compatibility with Android / iOS is indicated. All this information and which ones are better to buy I learned from SheWorn
To connect a wrist device and a smart on Android, you will need to install additional utilities on your phone (Wear OS by Google, BTNotification or others).