Not the same as the fliphone solution and won't allow messaging, but you can use lockmeout.online to create a random phone unlock code with a specified timelock

Not the same as the fliphone solution and won't allow messaging, but you can use lockmeout.online to create a random phone unlock code with a specified timelock. Carrying around a locked phone without knowledge of the unlock code still allows you to use the camera, take incoming calls, and everything you can do via Siri (i.e. make outgoing calls). But its meant more for short-term distraction-free durations (days, not months). Disclaimer: That service is a non-commercial side-project of mine.