If you took all the necessary precautions and no shortcuts on safety when putting your op together you should be fine. For example, wrapping your electrical connections only in electrical tape with out using a wire nut, or not properly grounding it, or using the wrong type of wire. Its always the little things that get you. I feel completely safe with mine running and no one home. If you add a device such as what your post is about, in my opinion you are actually adding something that could be a point of failure. If that thing starts going flaky on you, it could start turning your lights on and off and you may not know it for sometime and then your crop is damaged. Its just an unnecessary expense and possibly a point of failure that would not have happened otherwise. You know, KISS.