Heh, I was rather joking:) But sure, it is possible - you could use microphone, any amplifier (for example computer or something) and a speaker. The other way is yeah - disasemble the camera and connect its speaker cirquit to the aplifier directly (without microphone).
I guess first is much better idea.
And maybe much better would be to use LED on the front of the camera - so called autofocus led. Let it blink a few times before you start movie, therefore you'll know it has started. This requires a little scripting:)
