Working at a desk is destroying my posture, any good app to fix that?

I work on a 50/10 principle. 50 minutes work, 10 minutes stand/walk/stretch/yoga/light physical motion/workout. This has really helped me outside of simple posture (chest forward, chin back), proper monitor height, and holding phone at eye level.

I say try the pomodoro technique. Once you finish each 25 minute interval, stand-up and stretch during your break. I have at timer at simplepomodoro.io. Try it if you'd like.