The half-hour is the classic “don’t sit too long” beat: it is the interval ergonomics advice most often points to for standing up, moving, and resting your eyes after a stretch of focused work. Unobtrusive enough to leave running all day and still do its job.
Eight reminders cover four hours out of the box — extend it across a full workday, or trim it to a single focused session. Because it is so easy to ignore until it sounds, it is the one most people leave running from morning to evening.
A calmer quarter-hour beat — a beep every 15 minutes, on repeat, to stretch, sip, or check in at a desk or in class. Free in your browser, no sign-up.
A 20-8-2 sit-stand cycle: 20 minutes sitting, 8 standing, 2 moving, on repeat. A beep marks each change. Set the rounds for how much of your day it covers.