Self-explanatory.
Obviously for detecting turret movements on vehicles (including static) because there's no what I would call reasonable way to do this currently.
"Self made event" requires perframe handlers on all vehicles so not exactly great.

There's already PeriscopeElevationChanged so y no have this one too 🤔

Something like:

tank1 addEventHandler ["turretMoving", {
	params["_vehicle", "_turretUnit", "_currentRotationDeg", "_currentElevationDeg", "_turretClassName", "_turretPath"];
}]