For people who don't need to be actively locked out of their computers in order to have the sense to take a break, but still often forget to take a break for ho

For people who don't need to be actively locked out of their computers in order to have the sense to take a break, but still often forget to take a break for hours: Search for an 'hourly chime' app on your smartphone, have it go off every hour on the hour with a nice big ben or similar sound. This works for me, anyway. Most of the time.