I actully think about the fox puck every now and then, like when they go to 50 different replays to see if the puck is over the goal line. if they changed the fox puck technology a bit they would not have to wonder. if the puck is completly over the line a microchip in the puck could tell them. thats what i think but then again i could be way off.
It's a slightly harder problem that it appears.
Unlike with a soccer ball, pucks aren't spheres. If a soccer ball has a 12" diameter and a sensor in the middle of the ball shows it is more than 6" over the line then it's a goal.
But a 1" thick hockey puck on edge can be completely over the line as soon as it's centre is more than a 1/2" over. But if it is flat then it isn't a goal even if it is 1" over the line. Which means you need to record not just the puck's position but it's orientation, with a very high degree of accuracy (much better than the Fox technology did).
I have no doubt it's possible. And if they ever do it I'm sure it will be a great surprise the first few times a goalie makes a great glove save deep in their trapper and the goal light goes on.