Here's the deal. On DSLRs these days, the camera can be automatically triggered to take a picture of when a certain color moves assuming the lense sees it. They can use it on the ball. It is easily applied to freezing a video frame when a pass comes through. This would work well especially if the camera is overhead the line with the ball in its site. Manually tracking the defensive line overhead is easy, especially with the tech we have today. If the camera doesn't spot the ball, we can have a second camera tracking the ball to trigger a freeze frame on the camera tracking the line. The TV crew already pay for this technology. Plus, it's not hard. It's just we won't have the split-second flag-raising on close calls. There would be more like a 1-3 second flag-raise, which I would rather have than a wrong call. This would require 1-2 new officials affecting the game course.
There are probably better ways to do it, but yeah. Also, handballs in the 18 yard box can be whistled instantly as long as there's a ref watching the big screen and a couple cameras giving a good view in the box. It would be an instant whistle with those. Same can be applied to freakin' goal line technology. It's depressing to see that the fans have the ability to make the right call instantly (assuming different camera angles to the TV broadcast; look at the England-Germany game in the WC this year), when the refs on the field don't see the blatant stuff. Good thing the England-Germany match was one-sided before the game started.