Isn't that always going to be a bit too "after-the-fact" to be useful; i.e. it tells you that the market WAS trending, or WAS choppy, but doesn't give you any hints about what it might be about to do now (when you are trying to decide whether to go forward with a trending, versus a choppy, set up) ...Quote from Bolimomo: Eye-ball your charts.
Quote from piezoe: If you plot the up volume on the NYSE versus the down volume as two separate lines and do the same for the Nasdaq, you will see on choppy days that the lines continuously diverge and converge ocassionally touching each other, crossing, and interweaving. On trending days one line stays above the other and the lines tend to diverge as the day wears on.
Quote from Fleming Snopes:
You will trade better if you forget about everything but identifying support and resistance. Chop can "trend" and trend can "chop." What counts is where they last were and where they want to go now.