Pretty simple. I made an empty level with simple cycling animation. And this code, attached to object.
private AsyncOperation ao;
void Start()
{
ao = Application.LoadLevelAsync("Level1");
if (ao != null)
{
//GUI.Box(new Rect(0, Screen.width - 40, ao.progress * Screen.width, 40), "");
Debug.Log(ao.progress.ToString());
}
}