There is an example of using a callback in the Unity Integration Demo project. Check the MarkerCallback scene. But in short, it works the same way as in C++. For example:
AkSoundEngine.PostEvent("MyEvent", gameObject, AK_EndOfEvent, MyCallbackFunction, myCookieObject);
void MyCallbackFunction(object in_cookie, AkCallbackType in_type, object in_info)
{
if (in_type == AK_EndOfEvent)
{
AkEventCallbackInfo info = (AkEventCallbackInfo)in_info; //Then do stuff.
}
}
You can find more info in the Unity doc that comes in the Unity package, or in the AkCallbackManager class, or in the SDK doc (comes with the Wwise installation). Also note we have another Unity demo project for the 2014.1 version that also demonstrate the use of callbacks. Check it out!