I don't know how that watch works with your phone, which is why I suggested reading the manual carefully. Some of these watches may have their own app in the Play Store (or downloadable from the manufacturer's site) that will allow it to link with your phone. But since it's a standalone device, as long as you're logged in with your usual Google account, it should be able to notify you about a lot of things related to your Google account. The main thing that an app might help with is notifications for text messages and phone calls on your phone, since the watch would have a SIM with a different phone number.