As more time is spent diving into the details of Google's Pixel 2 and Pixel 2 XL, the handsets are continuously revealing some of their more unique features and secrets. With that said, it appears that supported Bluetooth devices can now report their battery life to both handsets.
While this is certainly convenient, Google doesn't make it easy to display these values at a glance, instead, requiring users to dig a little. If curious, you can head to the Bluetooth menu where paired devices are listed to get a peek at power levels or head into the device's details menu. This hasn't been tested on all Bluetooth headphones, so if you don't see battery life being reported on your unit, don't fret.
Android Police did note that there looks to be an ongoing notification for battery life when Pixel Buds are connected but this could be exclusive to the Google headphones or the notification hasn't been updated to work with Bluetooth headphones from other manufacturers. Naturally, as time passes, things could change.
Source: Android Police