To battle the ever rising use of your mobile, to the point where it literally interrupts your life and existence in the real world, iOS 12 will come with a new feature called 'Screen Time'.
Firstly, 'Reports' will show you how you use your device. This includes detailed breakdowns on what apps are used, when and for how long. Next is 'App Limits', a feature which helps aid you cut down on certain apps that can eat away at your time. You can set a daily time limit on apps you tend to get a bit addicted to and once the limit is reached, your iPhone will advise you that your time is up for the day.
This is really useful for your children, to prevent them overusing their devices. You can monitor their use as well as set allowances, by categories or particular apps. You can also limit access at certain times such as bedtime