Use a display calibrator with Arduino for bad sight

Hi,

I had an idea to make a sound notification when someone is over my crosshair. There is already a visual feedback for that purpose, but the only crosshair that gives you this option, also is immensely big and more in the way than helping me.

So what I had in mind was using a display calibrator on a second monitor that reads the pixels, the second monitor will display the same as your main monitor, and when a certain shades of colors are read by the display calibrator, an Arduino board uses that information and relays it to your computer, giving you a sound notification.

Would something like this be possible? If not, what else could one use to get accurate data to read the pixels on your screen?

I think you need to step back and start from the beginning. I've read this post about 3 times now and still don't have a clue what you're talking about.