Plastic instruments have already come and gone. Motion control feels like it never quite fulfilled its potential. The Oculus Rift, though still in development, has serious flaws. The Wii U and its tablet controller haven't been able to get off the ground. The gaming industry is looking for a new method of immersion, and so far nothing has taken hold. Now, Valve is looking into tracking your sweat with the goal of enhancing your overall gaming experience.