Safe Eyes is a little application that will interrupt you at set intervals and make you do some eye exercises for a few seconds or go for a walk. Default is 15 minutes for a short 15 second break or 75 minutes for a walk break but it's totally configurable.
To install for Debian testing/unstable it's simply
apt install safeeyesFor Debian stable there's a couple extra commands to install with PIP. For that and other distros, refer to the Installation section at https://slgobinath.github.io/SafeEyes/
I just installed it and love it already. I tend to get stuck in my chair staring at the screen for way too long!