Market Monitor is a breadth indicator. I developed Market Monitor after studying the breadth indicators commonly used. There are number of breadth indicator in the market and to get a comprehensive idea about them you should read The Complete Guide to Market Breadth Indicators by Gregory Morris.
Some of the popular breadth indicators are:
Advancing - Declining Issues
The McClellan Summation Index
New Highs-Lows Cumulative
New Higs-Lows Ratio
If you are Telechart user , you will notice it contains 28 different kinds of breadth indicators.