My laptop buzzes loudly if I slouch or put my hands on my face. Minimal effort implementation; damianmoore/tensorflow-image-classifier, fswebcam, cron, aplay.
fswebcam --no-banner capture.jpg \
&& classify.sh tf_files classifier capture.jpg \
| head --lines 1 | grep --quiet '^slouching\b' \
&& aplay buzzer.wav