Really cool! I did try One Sec, but actually setting up the shortcut to divert is quite tedious, and it only works at the point of opening the restricted app.
I like the UI, just wondering if the 'Breathe' prompt will get old quite quickly. I created an app (https://www.lungy.app) that tries to make each breathing session feel very different, hopefully making it feel fresh each time - I wonder if more variation would work in this case too.