thumb-sucking hints

like i said in an earlier post, we are working on getting kate to stop the habit of thumb-sucking. she seemed pretty gung-ho about it at first, but it seems like she is reverting a bit. she is pretty good about it during the day, but at night or nap when she is really tired, so does it automatically. i tried the nail-biking polish, but that doens't help at all. do you have any ideas or things that have worked for you? i have no idea what will remind her while she is sleeping. PLEASE HELP!!!