This is an indicator featured in one of Ernie Chan's mean reversion strategies. The Hurst Exponent will analyze a time series and determine whether it is a geometric Brownian motion, mean reverting or trending. This could be useful as a filter (to avoid whipsaws for example) or for offline analysis (such as data mining mean reversion opportunities).

The Hurst calculation considers a value > 0.9 to be trending, but as this appears to seldom be reached, I have designated it a "StrongTrend", whereas anything that exceeds the limit of geometric Brownian motion is a "Trend".

If there's any enthusiasm towards general utility I will submit a PR with unit tests.