TestWait.cs

using UnityEngine;
using System.Collections;

public class TestWait : MonoBehaviour {
    private bool hasTouched = false;

    public IEnumerator Start() {
        Debug.Log("1");
        yield return StartCoroutine(WaitForInput());
        Debug.Log("2");
    }

    public void OnTouchBegan() {
        hasTouched = true;
        Debug.Log("touched!");
    }

    public IEnumerator WaitForInput() {
        while(!hasTouched) {
            Debug.Log("waiting...");
            yield return null;
        }
    }
}