Vibrations can cause contractions! Which I guess is obvious, but damn it caught me by surprise. I was playing Destiny on my xbox and resting the controller on my belly. Controller was vibrating for a good bit because of a boss and I got a few pretty good contractions. Freaked me out at first, I thought I'd hurt him! They stopped as soon as I stopped playing though, but maybe you ladies can figure out a way to use this info!