Rather than set cameras or lasers on the uprights, I would suggest the
Hawk-Eye system that is used in sports like cricket, tennis, and soccer. It uses fixed point cameras throughout the facility to triangulate the path of the ball to within 5 millimeters.
But, this seems like overkill for a single call that rarely needs to be reviewed in NCAA football. If it could be used to determine if the ball broke the goal line or perhaps the line to gain, it may work. But, I'm not sure it could do that when the ball is in a pile of bodies.