I’ve set my shell to discreetly play the sound of a mouse button click upon completion of any command that ran for longer than 20 seconds. That choice of sound has the convenient effect that no one else seems to consciously notice it.
_click_preexec() {
_click_start_seconds=${_click_start_seconds:-$SECONDS}
}
_click_precmd() {
[[ $+_click_start_seconds ]] || return
if (( SECONDS - _click_start_seconds >= 20 )); then
pw-play 'mouse_click.wav' &!
fi
unset _click_start_seconds
}
preexec_functions+=(_click_preexec)
precmd_functions+=(_click_precmd)