With so many "S&P 500" bulls in the market not only is the volatility of the "S&P 500" very very low as of Monday, August 23, 2016, as shown on the screenshot below. The volatility of the VIX (the VVIX index colored in red) is also below the average right now. And the "VIX" index itself closed Monday at 12.27 points.
With the S&P 500 near record highs this gives me the idea that "VIX" ETFs like the VXX or VXZ might be something to watch ahead and after the FED related speech by Janet Yellen later this week. Here is an overview of "VIX" "ETF" products: firstbridgedata.com/page/list-of-vix-based-etfs/
And finally here is the screenshot showing the current very very low volatility of the S&P 500, which could be a sign that a trend change might occur soon. In case of a sharp decline this could mean a rising VIX index.