Why and When to Use a Stereo Mic on a Camera | Audio Insights (http://pro-audio.bhinsights.com/content/why-and-when-use-stereo-mic-camera.html)

Audio Technica Pro-24CM - would this get decent sound on T2i ???

should sound good. i've had good (better than the native mic) results with a similar sony.

that said, i'd also advise going double system - recording your mission-critical audio to an external recorder like a zoom h4, h4n...