During the development of the PlayStation 4's DualShock 4 controller, Sony tested a version of a controller that included biofeedback sensors to detect how stressed the player was, based on how much his or her hand was sweating. That's right; the same technology that's used in polygraphs could have been an integral part of the PS4.
We had a long research project where we looked at pretty much any idea we could think of. Would it help to measure the galvanic response of the skin? We tried out a tremendous number of things—and then we went to the game teams to ask them what they thought they could use from the controller.
The final version of the DualShock 4 controller, of course, features a touchpad, light bar, and improved triggers and joysticks. Body-monitoring features are not exactly a new thing, though. Nintendo's had heart-rate monitoring since as far back as 1998, and the Wii has an optional, little-used vitality sensor.