This is an "old" indicator by swingman - called RT_HourRanges Osc_v4 (you can find it on ForexFactory)
It basically tells you when (statistically which hours of the day) volatility is highest for an instrument.
It is - maybe - not up to date because it is not tick based.
For the Dow it looks like this:
(If you run it on your computer displayed times - of course - may/will change depending on the time zone you're in.)