The Rate Of Change Divergence indicator is used to identify a possible Bullish Trend Shift.
The rules are:
1. ROC(10) is rising. 2. ROC(30) is falling. 3. RSI(14) < 50
When all the rules are triggered this is indicated with a blue circle below the candle. Note that this doesn't give you a Buy signal; you also have to get a confirmation from the price graph, e.g by crossing a trend line.
This has become a favourite indicator of mine. I think it gives a very strong indication that a Bullish trend shift is in the making. I like to use it together with the Pocket Pivot indicator.