[adciv]

Alright, lets say "Red" is no job and "Green" is job. I'm also assuming the buttons for this are in fixed locations on the screen.

Setup all the tablets on a table, point a USB webcam at the tablets. Apply an HSV filter to what the camera sees to detect Green. All buttons are maped to a grid that corresponds to the pixels in the camera. In this way, when green is detected, the system knows which button is green.

Hard part: Get a device that lets you replicate a human touch. Stick these over every button on the screen. Whenever you get "Green" at that button, activate the device corresponding to it.