Sometimes I can't get my phone on fast enough to catch the unexpected action that happens in front of me. Below is a link to a list of apps that allow you to quickly turn on your phone video recording. I think I am going to try the one with a motion activation so I can just shake the phone and it turns on video recording.
http://gadgetstouse.com/gadget-tech/instant-video-recording-on-androdid/20934
http://gadgetstouse.com/gadget-tech/instant-video-recording-on-androdid/20934