Is there a way to detect a button push (for instance the camera button) when the phone is locked and have something happen, like run a script?

What I would like is to be able to reach in my pocket and push some button and have the phone vibrate for a moment if there are any notifications, so I don't have to pull the phone out and look for the light. I think it'd be a nice little feature. Could be a little code in the vibrations -- two buzzes for text messages, one for emails, something like that.