Pixel's "At a glance" widget available now to those beta testing the Google app for Android1
While tapping on the weather did take us to Google's weather app, tapping on the date on the left won't bring you anywhere unless you have a calendar appointment in the Google Calendar app. If you do, the appointment will show up in place of the date and weather on the top of the widget. A second line will appear in smaller print showing you the location of your appointment. Next to that will be the weather information (check the slideshow for a screenshot). Google's intentions are unknown at the moment, and the ability of non-Pixel phones to use this widget could end when the final version of this update reaches the public version of the Google app.
For now, if you are a beta tester for the Android version of the Google app, make sure that you're running version 8.1. If not, head over to the Google Play Store and open it. Go to the hamburger menu in the search field and tap on my apps & games. Check to see if the update to the Google app is waiting for you. If so, click on the "Update" button. Once the latest version is installed, check out the Google widgets available for your phone. You should see the "At a glance" widget ready for you to slide on to your phone's screen.