Update 8/7/18: According to several users, this mod also works on the OnePlus 6.

Right after Digital Wellbeing, Google's new anti-smartphone addiction feature introduced at Google I/O, started rolling out for the Google Pixel and Google Pixel 2 on the latest Android Pie release, we managed to get the feature up and running on the Essential Phone which also received Android 9 today. Digital Wellbeing is actually quite easy to port to the Essential Phone and other non-Google devices running Android 9 simply because the APK itself doesn't need any changes whatsoever—just enable the right platform features, set the right permissions in the right place, and you're good to go. So long as your Essential PH-1, OnePlus 6, or other non-Google device on Android Pie has root access via Magisk (the current version already works on Android Pie), all you have to do is install a Magisk Module to get it up and running.

Recommended Reading: Digital Wellbeing now live for the Google Pixel/Pixel XL & Google Pixel 2/Pixel 2 XL

After I figured out the necessary steps, I asked XDA Senior Member Dil3mm4 to turn the process into a Magisk Module, so many thanks to him for helping out! We also got help from XDA Recognized Developer Maxr1998! Here's the Module, followed by an explanation of how we got it working for anyone who's curious:

Download Digital Wellbeing Enabler for Android Pie

How we enabled Digital Wellbeing on the Essential Phone/OnePlus 6 running Android Pie

The app came pre-installed on the Google Pixel smartphones starting in the second Android P Developer Preview, however, it was a placeholder and wasn't actually functional. Today, Google opened up a beta program for the app on the Google Play Store and started allowing Google Pixel owners to download an update to the placeholder app. We pulled the update APK and examined what it required to run. All it needs are:

  1. Android Pie (Android 9)
  2. com.google.android.feature.WELLBEING defined as a platform feature (solved by adding an XML defining it in /system/etc/sysconfig)
  3. com.google.android.feature.PIXEL_EXPERIENCE defined as a platform feature (solved by adding an XML defining it in /system/etc/sysconfig)
  4. Installation as a privileged system app because of some of the permissions it requires (such as the new Android Pie permission android.permission.OBSERVE_APP_USAGE)
  5. Defining the privileged app permissions it requires due to restrictions introduced in Android 8.0 Oreo (solved by adding an XML defining them in /system/etc/permissions)

Because #2-5 require modifying the system partition, getting Digital Wellbeing on the Essential Phone or OnePlus 6 requires root access. For those of you who don't want SafetyNet to fail, we made the Magisk Module so you won't have to sacrifice Google Pay or Pokemon Go just to get the Google Pixel's Digital Wellbeing feature working on your Essential Phone or OnePlus 6 running Android Pie.

This article was updated to reflect that this mod also works on the OnePlus 6.