Seattle-based designer Sam Matson developed a headset that tracks "gamer rage" and adjusts a custom game's difficulty to compensate for it. Dubbed "Immersion," Matson's headset uses an optical sensor that reads "minute color changes in the user's ear tissue to approximate a pulse."
Matson's prototype headset includes both audio input and output channels in addition to the heart rate monitor, relaying information via bluetooth to a hacked Xbox 360 controller. He developed a custom shooter game using Unity that ramps up the difficulty as the player's heart race increases, encouraging the player to stay cool and collected. The Immersion headset isn't a commercially available product, and it's uncertain if it ever will be, but Matson does offer a few glances at the prototype model on his website