Please excuse me if I fall into the trap but Sabre Zero 1 has clearly misread the instructions on his model kit! I'm still trying to work out what a pencil lazer is?
However, the Apache Pilot has a system called the IHADSS (Integrated helmet and Display Sighting System) which once the Helmet is boresighted to the Ac, can then act as a sight. The Gun when actioned is then slaved to the Pilots helmet and follows head movements within it's available limits.
This is achieved through IR connectivity and algorithm calculation of head movement and positional timing.
So to answer the original question 'what connects the Apache Pilot to the gun?',.. Black box technology.
There is always the possibility of the Pilot forgetting he has the gun actioned and causing a blue on blue and I believe there are recorded instances. Good drills and training discipline help to negate fratracide but the human interface is usually the weak link!