The Intraday Momentum Index (IMI) is calculated like the Relative Strength Index(RSI) but uses the relationship between the intraday opening and closing prices to determine whether the day is up or down. When the close is above the open, it is an up day. If the close is below the open it is a down day. 

As with the RSI, overbought conditions (and lower prices ahead) are indicated when the index rises above 70. Values below 30 indicate a potential oversold situation and higher price ahead.

Remember, as with all overbought/oversold indicators, you should first quantify the trendiness of the market before acting on any signals.

Developed by Tushar S. Chande and Stanley Kroll, the IMI is published in their book “The New Technical Trader” dated 1994.