I managed to build myself exactly this with Claude's help. There are 3 levels of protection.

1. I use an app called SelfControl, which blocks websites temporarily.

2. I have a script which watches `/etc/hosts` with launchd and reverts it to a version pulled from a server if the file changes. This blocks websites I never want to go to.

3. I setup a 'focus mode' with hammerspoon prevents me from launching certain apps, and makes me wait 30 seconds and type a string of text when I want to switch it off.

Yes, all of these things can be disabled when I want to, but the point is that they all add some fiction and give me a chance the reconsider the distracting action I was about to take.

I've been doing it for about 2 weeks, so far it's working pretty well!