CCTimeDelay::Create(3f), /* 3 second delay */
CCCallFunc::Create(…void* to your func)
What you do in your callfunc can be your timer callback.
CCNode::Schedule(func, delay). This will call your func every delay seconds. If your app goes to sleep, just pause the director, and then when it resumes, you resume the director. If you do that, cocos2d will do the rest for you.