Reactive Grip is an interesting technology by Tactical Haptics which lets you feel feelback from games in the palm of your hands. The company plans to take their prototype to Kickstarter to raise money for production versions of their controller. They say that motion component of the controller will support Sixense STEM and other trackers.
I got to try Reactive Grip for myself at GDC 2013. I was definitely not expecting a few sliding bars on the grip of a controller to be able to provide a number of compelling sensations, but they certainly did. Here’s a video of me checking out a prototype of the system: