The above image capture shows the trendline touching three points, and at the right corner the price breaking below the trendline.
Potentially the index will go down all the way to 1,671, or 1,796.
ETFs to play this:
ONEQ is a Fidelity ETF that tracks the COMP, and the popular QQQ is closely related (it's the Powershares version of Nasdaq 100 index). Here are the charts for both of these showing trendlines and their corresponding Fibonacci levels (please watch video for the meaning of those).:
You can use this tool yourself through a trial.