https://medium.com/@kevinrose/disconnect-and-take-a-break-from-your-iphone-by-using-this-little-known-feature-c8e6f41660da

Having device fatigue? Need a break from the screen?

Right now, hidden in your settings, your iPhone has a feature that locks down your phone, making it unusable, while you get a much needed break. When enabled, this setting also automatically replies to your texts, letting your friends know that you’re offline.