How to Intercept Unity "Save Scene As.." right after saving?

Answering my own question, I had to create a Singleton and fill the FileSystemWatcher delegates:

 [ExecuteInEditMode]
 class SceneNameSingleton : MonoBehaviour
 {
     private FileSystemWatcher m_SceneFileWatcher;    // This watches to see if we have saved the level
 
     private static SceneNameSingleton instance;
 
     static GameObject genericSingletonGO;
     public static string SINGLETON_NAME = "Singleton";
 
     public static SceneNameSingleton Instance
     {
         get
         {
             if( instance == null )
             {
                 if( genericSingletonGO == null )
                 {
                     genericSingletonGO = GameObject.Find( SINGLETON_NAME );
                     if( genericSingletonGO == null )
                         genericSingletonGO = new GameObject( SINGLETON_NAME );
 
                     
                 }
 
                 if( genericSingletonGO != null && genericSingletonGO.GetComponent<SceneNameSingleton>( ) != null )
                 {
                     instance = genericSingletonGO.GetComponent<SceneNameSingleton>( );
                 }
                 else
                 {  
                     instance = genericSingletonGO.AddComponent<SceneNameSingleton>( );
                 }
             }
             return instance;
         }
     }
 
     void OnSceneFileWatcher_Created( object sender, FileSystemEventArgs e )
     {
         if( e.FullPath.Contains( ".meta" ) ) return;
         if( !e.FullPath.Contains( ".unity" ) ) return;
 
         Debug.Log( "OnSceneFileWatcher_Changed" );
         string sceneName = System.IO.Path.GetFileNameWithoutExtension( e.FullPath );
         Debug.Log( "File: " + sceneName + " " + e.ChangeType );
     }
 
     void OnEnable( )
     {
         Debug.Log( "OnEnable" );
         m_SceneFileWatcher = new FileSystemWatcher( Path.GetFullPath( "Assets" ), "*.unity" );
         m_SceneFileWatcher.Filter = "*.*";
         m_SceneFileWatcher.NotifyFilter = NotifyFilters.LastWrite;
         m_SceneFileWatcher.EnableRaisingEvents = true;
 
         m_SceneFileWatcher.Created += new FileSystemEventHandler( OnSceneFileWatcher_Created );
         m_SceneFileWatcher.Changed+= new FileSystemEventHandler( OnSceneFileWatcher_Created );
     }
 }
 

This way everytime a unity scene is created or modified it'll be detected and logged.