This is a good point. And I think this may be the key. Finding some way for the alert to get up and walk every half hour be not a distraction, just something you react to without breaking concentration. Because I can totally see myself just hitting cancel and getting up and walking without changing what I’m thinking about if the alarm wasn’t toi obnoxious. I already to that for certain alerts
Practice with this will help you. So, at first - it may distract you, but with repeated practice, you'll be able to sustain your focus even as you go for a walk.
