Keltner Channels is the most simple and most effective timing indicator. You should watch the video below in which Chuck Hughes explains how he uses Keltner Channels for timing his trade entries and exits.
Chuck Hughes is a master stock options trader. He has been consistently making high returns with low risk. You should also watch this video in which Chuck Hughes explains his timing indicator in more detail!
Keltner Channels are just a combination of 20 period EMA and 10 days ATRs above and below this 20 period EMA. You can also read this article on Keltner Channels.