At work we have a big TV screen with a build status being displayed. The desktop support team had a large lead time on changing the settings to stop it locking the machine every 5 minutes. This was the temporary workaround.
The java.awt.Robot has a few other interesting methods like taking screenshots, getting the colour under your cursor and clicking the mouse.
This code has no dependencies.
I’ve compiled a version using Java7 which you can download and use right away.