Android phone is required. iPhone compatibly for Samsung watches is planned in a future update, pending Samsung adding the appropriate API to support 3rd party apps with iPhone connection.
Standalone mode and club entry are available for Tizen smartwatches, including Gear S3, Gear Sport, Galaxy Watch (1-3), Galaxy Watch Active (1-3). See this article for more details about the available features.
If you have the original Gear watch (model SM-V700), you need to ensure it runs the latest Tizen firmware (this watch originally shipped with an older Android firmware). Please refer to this page for firmware upgrade instructions.
Note, Samsung Galaxy Watch 4 and Samsung Galaxy Watch Active 4 running Wear OS are supported. Click here to learn more.