The original note, as written at the time
We could think of an internet limiter for all users. For example, internet use can be limited to one hour a day. This could be set for a single device or all devices or a set of devices. This can also help to curb the issue of internet overloading. A variable number of messages per day can be set to better structure the balance. This service can be set to be free for whoever chooses to be part of the project.
Ongoing development
A limiter available to every user: internet use restricted to, say, one hour a day — set per device, or across all devices, or a subset. A variable for messages per day can also be set, to structure the balance better. Free to anyone who chooses to join it.
The important word is choose. Everything we currently have is either unlimited or a parental control, and a parental control is a thing imposed on somebody by somebody else.
A voluntary limiter is a different object: a commitment device. It works because the decision is made once, in a calm moment, and the person who made it is not the person who has to live with it at eleven at night. That is the whole mechanism of every commitment device ever built, from a gym membership to a locked drinks cabinet.
Doing it at the network level rather than per app is the right scope, and it is the one nobody offers. Per-app limits treat the symptom; the hour you lose is rarely in one app, it is in the drift between five of them.
The messages-per-day variable is the more interesting control, because messages are the unit that actually costs attention. An hour of reading is restful; forty messages is work. Limiting the count rather than the clock matches what is being spent.
The design has to survive the person it restrains. There must be a way out, or people will not sign up; and the way out must be slow enough to be a decision and fast enough not to be a prison. A twenty-four-hour delay on cancellation is probably the right shape.
Free for whoever joins, because this is public health, not a subscription.