Do you mean a rail docker? If so, yeah that would be handy.Much like rails can send signals when docked on, a docking module should be able to send a logic signal while attached to a rail. I think this would be a very useful feature for automating docking procedures.
In that case, let me revise my suggestion. It would be really nice to be able to slave logic blocks to rails and rail dockers.They can activate buttons and switches adjacent to them.