https://www.theverge.com/circuitbreaker/2018/3/29/17176080/google-wear-os-developer-preview-android-p-better-battery-life

Yesterday, Google launched a developer preview for Wear OS (formerly Android Wear) a few weeks after releasing the first Android P preview for smartphones. Just like that initial build, this software for the company’s wearables platform remains extremely unfinished, and Google flat out says it “is not for daily or consumer use” at this early stage. For now, it’s available exclusively for the Huawei Watch 2 Bluetooth and Huawei Watch 2 Classic Bluetooth, and the preview build must be flashed onto the device manually — another indicator that it’s meant strictly for developers and not your average tech enthusiast.

The biggest changes in this first release are meant to preserve battery life. “To improve power, apps will no longer be allowed to run in the background unless the watch is on the charger,” Google said in its blog post. There are two exceptions to that rule: watchfaces and complications currently chosen by the user can continue to run in the background.