GUITextureButton

using UnityEngine;
using System.Collections;

[RequireComponent (typeof (GUITexture))]

public class TouchButton : MonoBehaviour {
	public GUITexture theButton;

	void  Update () {
		if (Input.touchCount > 0) {
			foreach (Touch touch in Input.touches) {
			    if (theButton.HitTest(touch.position)) {
					DoSomething();
				}
			}
		}
	}
}