I would imagine you could watch /dev/psaux for changes. Go grab an old ball mouse take the ball out and use
Then start clicking away and see if the screen is updated, also make sure that it doesn't get updated if the mouse is just sitting still. If it is being updated only with clicks then you would need to use
stat --format=%Y /dev/psaux
in a script that runs as a cron job every few seconds or what ever is needed.