I've been using stochastics as an approximation of the 7-8 day cycle. Used in concert with a trendline, it has been providing fairly reliable signals.
It's important not to frontrun it however, in the event that the market trends due to a larger cycle (I watch daily charts to get a sense of the larger prevailing trend).
Here are some examples from the energy complex:
As you can see, things look just about ready for a downturn. This is scam week however, so I wouldn't be surprised to see things pinned at these levels. Next week, I would expect the downside to begin. (Typically at these inflection points, I would expect to see either a gap n' crap to trap a few bulls, or simply a gap down to prevent bears from getting in at the peak.) Nevertheless, I will wait until the cycle clearly turns and the trendline is broken.
Well, in theory at least. Realistically, I'll probably frontrun it and get torched.