Introduction: This gem is straight out of chapter 9 of "Short Term Trading Strategies That Work" by Larry Connors and Cesar Alvarez. In the book, the authors discuss the creation of a custom strategy that sums the past X bars of the regular Relative Strength Index indicator, and they discuss how this modified "cumulative" RSI provides better entry and exit points.
How it works: This indicator sums the past X periods of the Relative Strength Index, and plots this "cumulative" measure of the RSI. Since the cumulation changes the score scale, the upper and lower bands are dynamic based on how many bars back you are summing for the cumulation. The upper and lower bands are adjustable with an input, along with the RSI length and cumulation period.
Additional explanation: The authors use this indicator on the 1 day time-frame, typically with the RSI length set to 2 and the cumulation length set to 2. Based on how the indicator works, under those settings the current value would read the sum of the last 2 day's regular 2 period RSI. Test it out!