I am inclined to agree with the others than a technological solution is not likely what you need. The trick is to segregate these areas mentally, so that you are acutely aware of when you are "on forbidden ground". The "rubber band" trick has been mentioned here already, and it's based on helping to re-enforce that awareness. Technological solutions can help do this. Timer apps that give you a regular notice to "GTFO THE PHONE FOR 15 MIN NOW" for example, are building the same kind of awareness, just as a software tool to do so.

In my case these bad habits predate the iPhone's existence. What we call phone addiction now was the "Internet addiction" of 15 years ago. Some strategies that have helped me, I think:

One: The phone never comes to bed with me. It never comes out in real-life social interactions either.

Two: During the day I keep it physically separate from me if possible. In my drawer at work. Just on the table on the other side of the room here at home right now. Checking it requires physically standing up and walking over. More likely this will percolate up into conscious awareness.

Following from that, stand when you're on the phone. Don't sit down and slump and relax.

Three: Purge all the dopamine-ticklers. In my case, if you'll excuse the bluntness, that means: No Twitter or other clickbait feeds. No outrage-driven news. No porn. No hookup apps. No endless-browsing online shopping.

Hell, even Hacker News warrants some caution. You're just such a rewarding bunch.

And this is not just on the phone. In all of my life. As a general mental cordon sanitaire. I cross into the quarantined zone often, I must admit, but the key is to be aware, to have a niggling sense of unease, when you're in the danger zone. Check your dosimeter regularly and have a planned exit.