With the Ipad set to always on, could you do something with a heuristic image, one 1x1 pixel image (off) and one black one full screen size image (on). Then display the image based on a variable, with it set to the highest z order..
During the day the small image would be displayed giving you full access to the controls on the control page.
Set the variable to off at a certain time, and the black image is displayed, covering the controls. If the screen(black image) is touched the variable is set to off for x minutes to allow you to use the underling controls on the control page before being dimmed.
I'm not sure how bright a black image would be without testing, but have thought of implementing this a few times.