Eco-Gym
Many times I've thought while walking past these massive 24-hour gyms in Manhattan, seeing folks slave away on elliptical machines and treadmills, "what a waste of energy!" I'm not sure how the math works out, but someone (not me) should use that wasted power by starting a gym where all the energy expended during these workouts is stored for reuse. If humans found a way to reuse the energy they spend during exercise, it might lead to a healthier culture with cheaper energy. I envision a world where this practice becomes so standard that people could have energy bank accounts where they can ...