With Wear OS by Google, a watch has multiple ways to send and sync data. It is strongly recommended that you send and sync data directly from the network, rather than using the Wearable Data Layer API. (View Highlight)

Send and sync data directly from the network

Build Wear OS apps to communicate directly with the network. You can use the same APIs as you would for mobile development, but you need to keep some minor Wear-OS-specific differences in mind. (View Highlight)

Send and sync data with the Wearable Data Layer API

The Wearable Data Layer API, which is part of Google Play services, provides an optional communication channel for apps.

This API is only available on Wear OS watches and paired Android devices. For Wear OS watches paired with iOS phones, apps can query other cloud-based APIs if Internet connectivity is available. (View Highlight)

For example, when the user saves a note on a handheld, it automatically appears on all of the user's Wear OS devices. To help synchronize data between devices, Google’s servers host a cloud node in the network of devices. The system synchronizes data to directly connected devices, the cloud node, and to wearable devices connected to the cloud node using Wi-Fi. (View Highlight)