Hello,
Multistate tools basically allow you to easily switch the geometry of a tool, e.g. so that a gripper also shows the workpiece it's holding.
Regarding the gripper: If it's controlled via IOs then you can just toggle the IOs via KUKA|prc. If the gripper is using its own library, you can just "hack" a bit into the *.java code that is provided by us.
So that e.g. when you toggle output 5, it actually actuates the gripper via the library.
Best,
Johannes