OBSOLETE! Everything done here can be accomplished using the ExtensionMethods.cs definitions for MonoBehaviour

TimerManager.cs

using System;
using System.Collections;
using UnityEngine;

public class TimerManager : MonoBehaviour
{
    private static TimerManager _instance;
    private static TimerManager Instance
    {
        get
        {
            if (_instance == null)
            {
                _instance = new GameObject("Timer Manager").AddComponent<TimerManager>();
                DontDestroyOnLoad(_instance.gameObject);
            }

            return _instance;
        }
    }

    public static void ExecuteAfter(float seconds, Action action)
    {
        Instance.StartCoroutine(ExecuteAfterCoroutine(seconds, action);
    }
    private static IEnumerator ExecuteAfterCoroutine(float seconds, Action action)
    {
        yield return new WaitForSeconds(seconds);
        action();
    }
}