This indicator is based on the assumption that the price variations follow a multi-fractal model. From there, the Hurst exponent H can be easily computed from the fractal dimension (as obtained in http://codebase.mql4.com/en/code/8844). The variations of this Hurst exponent can actually be seen as predicting the variations of the volatility, and they therefore provide a time for entering into a trade (whenever this variation is positive), in order to profit from the high volatility period.
It must be noticed however, that this indicator doesn't give any information as to the direction of the trade, for that a directional indicator must be used.
For more details about this indicator, please see my blog: http://fractalfinance.blogspot.com/2010/05/variation-of-hurst-exponent.html
Here is how it looks like, in the lower window, on a 1hr EUR/USD chart:
The Acceleration/Deceleration Indicator (AC) measures acceleration and deceleration of the current driving force.Average Directional Movement Index (ADX)
The Average Directional Movement Index Indicator (ADX) helps to determine if there is a price trend.