Relative Strength Index, or RSI, is similar to stochastics in that it identifies overbought and oversold conditions in the market. It is also scaled from 0 to 100. Typically, readings below 30 indicate oversold, while readings over 70 indicate overbought.
RSI is a very popular tool because it can also be used to confirm trend formations. If you think a trend is forming, take a quick look at the RSI and look at whether it is above or below 50. If you are looking at a possible uptrend, then make sure the RSI is above 50. If you are looking at a possible downtrend, then make sure the RSI is below 50.