I was very surprised to know about this Google's attempt because tech giants like these normally work towards increasing the screen time of users so they can make more bucks.

This is an experimental thing and Google has released 3 different apps which can help you minimize your phone usage. These apps are Activity Bubbles, Envelope and Screen Stopwatch. The ideas behind all of these apps are very innovative.

Activity Bubble:

Whenever you unlock your phone to do something, this app running in background will create a bubble on your wallpaper. If you spend lot of doing during one task then bubble will get bigger accordingly.
At the end of day, you will be able to see many different bubble patterns formed on your wallpaper just giving you a rough sketch about how much you have used your cellphone for today.
I am sure, someday with neat wallpaper might give you pleasant feeling.

Envelop:

This is a very tricky app. It works on principle of actual envelop. You have to choose your most used apps and fold it into envelop form. At first, you will be able to do only primary phone tasks only but with time, you can do more and more stuff with it.

Screen Stopwatch:

This app works kind of like Activity Bubble but it displays a timer on screen whenever screen is unlocked and you are doing something. Timer automatically stops when phone is idle. It does give you continuous feeling of usage.