App Limits in iOS 12 lets users manage device time & parents set allowances
In introducing iOS 12 on Monday, Apple revealed a collection of tools designed to better temper how people use their devices, including App Limits, notification changes, and upgrades to Do Not Disturb.

iOS 12 Screen Time.
An addition to Do Not Disturb is "Do Not Disturb During Bedtime," which will prevent barrages of overnight notifications creating distractions. Instead notifications will be muted until the morning, at which point people can tap their screen to see what they missed.
Notifications will also be grouped by app, topic, or thread, much as on Android. A swipe will open options to manage or clear items en masse. Another feature, "Instant Tuning," will let people press into a notification and choose to turn off alerts from a particular app or push them straight to the Notification Center without hitting the lockscreen.
A new app, Screen Time, will deliver weekly activity summaries showing how much time was spent on a device and in which apps, as well as which apps send the most notifications. Critically, users will be able to impose limits on how long an app can be used, which will also sync between iPhones and iPads to stay consistent. Through Family Sharing parents will be able to create time allowances for children, including downtimes.


iOS 12 Screen Time.
An addition to Do Not Disturb is "Do Not Disturb During Bedtime," which will prevent barrages of overnight notifications creating distractions. Instead notifications will be muted until the morning, at which point people can tap their screen to see what they missed.
Notifications will also be grouped by app, topic, or thread, much as on Android. A swipe will open options to manage or clear items en masse. Another feature, "Instant Tuning," will let people press into a notification and choose to turn off alerts from a particular app or push them straight to the Notification Center without hitting the lockscreen.
A new app, Screen Time, will deliver weekly activity summaries showing how much time was spent on a device and in which apps, as well as which apps send the most notifications. Critically, users will be able to impose limits on how long an app can be used, which will also sync between iPhones and iPads to stay consistent. Through Family Sharing parents will be able to create time allowances for children, including downtimes.


Comments
If this works well then it is the best new feature in iOS 12 for many many families.
Fortunately, I'm the primary account so my wife can't use it on me.
Apple ticks to their own clock.
However it does give parents more control over their kids habits.
A smartphone is different because it serves so many functions. I want my daughter to take her phone to school in case we need to coordinate after-school transportation, but she doesn't need access to games during the school day. I also want her to use it to download and read library books, which she often does, especially when her social media allowance is used up for the day. If you simply take the phone away, you lose all the good functions, too.
Amazing, to say the least.
While you may be right that the most "effective" tool (in terms of limiting access) is taking the device away, it is not the most practical. A simple on/off switch could be considered the most effective method of controlling an air conditioner, but many models offer fine tuning via various settings that let the user not only enjoy the product in a way that suits them best, but also contribute to the betterment of society (lessening environmental impact). I don't think anyone is blaming the companies making AC's for society's ills, but the average consumer recognizes that having more control of the use of the product can enhance the experience.
A smartphone or tablet is incredibly useful and much more multi-purpose than a TV from the 80's or a gaming console (even the old ones like the Commodore that could be used for basic computing functions). Whereas nature or other learning style programs were and still are available on TV, the viewing of such programming was easily controllable just by limiting usage to the time of day that such programming was available. This is a key difference to a modern smartphone or other device that can access the "always-on" internet. Another huge difference is that the devices from the 80's you mentioned weren't exactly portable. When my parents said that we kids had watched "enough" they turned off the TV and we had to leave the TV room. This is not so easily accomplished with an item that can fit in your pocket and work anywhere.
I have been waiting for these tools to come along so I can start planning how to let my kids begin to use a smartphone. While I don't think it is fair to "blame" device manufacturers or content providers for failing to make in easy to limit the use of their products, it is a big selling point and factor to differentiate their product vs the competition. Successful tech companies will continue to improve in this and other areas not simply because the want to avoid blame for "device addiction", but because it is one more way to outsell the competition and serve their customer base. Parenting in the digital age is fundamentally different than it was when I was a kid living in rural Kentucky 30+ years ago, and I'm happy to have one more tool at my disposal to help me train my kids to use modern technology responsibly.
I am not saying that Apple’s changes are not welcome - they most definitely are & I will use them.
It is great to be able to lock the knife on the Swiss Army knife, but have the screw driver & toothpick still available.
I am eluding to the fact that many parents stunt the development of their child’s discipline by simply “giving up” control because the other options are “too hard”. But the fact remains that many parents themselves lack discipline, so it ends up being a
learned trait passed to the next generation.
Being a parent can be a difficult, time-consuming task, but when I think of the real-world places/situations my parents had to keep me away from as a child (I grew up in a city, roaming the neighborhoods between home, school & my grandparents houses) I don’t think it was *easier* that policing the digital places/situations my children are faced with. But if the parents are camped out at the corner store eating junk food & drinking soda, chances are they won’t be walking a hard line when their kids do the same.
I think your suggestion of adding a "simple cell phone" to an iPad is not well thought out. Not only is it more cumbersome than the OP's solution of an iPhone (because you would now need to manage 2 devices), but provides even less control and security. How many flip phones have really good control options (restricting calls to certain contacts and preventing the addition of new ones, blocking text messages from certain senders, preventing the deletion of call logs or message threads, etc.)? How many simple phones have a built in recovery feature like Find My Phone"? I can list several more ways this set up would be even worse.
Secondly, Guided Access Mode in many ways is insufficient for session control. Guided access mode locks access at is broadest possible application, to complete use of a single app (and of course can be fined tuned to lock out certain functions within the app, screen areas, etc.). There is presently no way to create a "folder" or grouping of any sort for apps that are kid-friendly (or in other words approved by the parent) that can then be handed over for "supervised" use. Locking an iPad to one app at a time and waiting until the kid finishes with the app to lock it to the next app is not only time-consuming and irritating, but in several situations impractical (like when parent is driving with a kid using a device in the back of the car).
I am actually still hoping for an expansion of guided access relating to resticted groups of apps because this would be very useful for "shared" device access (where a kid uses the adult's device for limited sessions). Many people will not buy a child (not talking teens or even pre-teens) their own device where it can be completely stripped of all "non-suitable" apps and functions, especially because of the loosening of control that providing a personal device would entail. Clearly the best solution is expanded software control possiblities for the idevices in question.
People work out all the time. Are they addicted to the gym?