In late 2017, Google launched an app to help you cut down on your mobile data usage called "Datally." Datally's already pretty great as is, but Google recently announced four new features for the app that aim to help you use even less data.
The feature that users will likely find the most useful is Daily Limit. With this, you can tell Datally how much mobile data you want to use each day. Once you hit that number, you can either keep using your data or block it for the rest of the day.
Another big addition is Guest Mode. If you've got a friend, kid, or someone else that wants to play around with your phone, you can use Guest Mode to enable a data limit before handing them your phone so you can make sure they only use the data you allow them to.
On top of Daily Limit and Guest Mode, Datally is also getting a map that shows nearby Wi-Fi networks and an Unused Apps tool that'll sniff out apps you aren't using but are still eating up your data in the background. Datally will then present these apps in a list, show you how long ago it was opened, how much data it's used, and give you a shortcut for quickly uninstalling it.
All four of these features are rolling out to the Datally app today on the Google Play Store.