Especially for iPad, it detects whether the device is moving or not

StandbyDirector.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

// Especially for iPad
public class StandbyDirector : MonoBehaviour {
    private Vector3 acc = Vector3.zero;
    private Vector3 oldacc = Vector3.zero;
    private float timer = 0f;
    private bool isFinished = false;

    // custamizable
    private float threshold = 0.02f;
    private float standbyTime = 5f;

    // Update is called once per frame
    void Update () {
	goStandByIfNeeded();
    }

    // if device doesn't move, standby
    private void goStandByIfNeeded() {
	acc = Input.acceleration;
	float diff = Vector3.Distance(acc, oldacc);

	if(diff < threshold){
	    timer += Time.deltaTime;
	    if(timer > standbyTime && !isFinished){
		isFinished = true;
		standBy();
	    }
	}else{
	    timer = 0f;
	}

	oldacc = acc;
    }

    public void standBy() {
	Application.LoadLevel("YOUR Standby Scene Name");
    }
}