The Stochastic RSI, as the name implies, is an Indicator of an Indicator. While the Stochastic Oscillator monitors relationships between closing prices and the range, the Stochastic RSI monitors the RSI values and their relationship over time.
The Stochastic RSI oscillator is calculated:
[ (Today's RSI - Lowest RSI in %K periods) / (Highest RSI in %K periods - Lowest RSI in %K periods) ] *100
As with the Stochastic Oscillator, the Stochastic RSI is usually accompanied by a second line %D which is an EMA of the Stochastic values. From this point the crossover events can be used to provide entry triggers as well as confirmation to other indicators.