A second output slot and a circuit signal that output the state of the beam, broken/unbroken, would be really cool. The laser could then be used as a trigger/switch in a circuit network. I'm not sure if trains block the laser but the modded logic carts and other vehicles do.

This could have a ton of uses actually. Stopping, starting, spacing, or forcing direction of logic carts and trains. Physical clocks and timers from carts or trains running a circle. Measuring how much time something spends waiting or force conditions like wait/go depending on how long a beam is broken or not. Could wire up a counter circuit that read the amount of times the beam is cut then trigger something off of that once the condition # is met, or just use it to track the amount of passes per X amount of time a train stop is used or an intersection or a specific line. Perimeter warning system and base defense stuff, that's if biters can interrupt the beam? Would even be the perfect finish line for a race track.

Add to that mix a beam recieving sensor with it's own output signals, plus a way for the laser to read out it's current beam length as a signal as well... And you've really nailed it!