親の親の親の...親からGetComponentしたい！！そんな拡張 ref: http://qiita.com/enpel/items/7d9eb414a92f15ea694a

file0.cs

using UnityEngine;
using System.Collections;

public static class GameObjectExtensions
{
    public static T GetComponentInParents<T>(this Transform obj) where T : MonoBehaviour, new()
    {

        Transform parent = obj.transform.parent;
        while(parent != null)
        {
            T res = parent.GetComponent<T> ();
            if (res != null)
                return res;
            parent = parent.parent;
        }

        return null;
    }
}