iPhone is compatible only with Apple Watch, Pebble and Magellan Echo. There is no support for Gear/Galaxy watches and Android Wear at this time.
iOS devices can sync with Samsung watches, however 'companion' apps are not supported. So one can download an app on the watch that runs completely independently and does not require a matching app on the phone. Golf Pad does rely on 'companion' app functionality: for example, a round has to be started or saved on the phone. This is true even when standalone mode is used during the round for rangefinder and shot tracking. When manufacturers add support for companion apps on iOS, we'll be happy to add Golf Pad watch app for iOS.