Lightweight, wearable gadgets have changed our workout routines. Some of us consider it an integral part of every workout to monitor our heart rates, activity and calories burned in real time. Future devices may become even more enmeshed in our fitness routines. Enter battery-free gadgets powered by body heat. If you run hard, bike for miles or work up a daily sweat, TEGwear technology will reward you with power. Perpetua, a company that specializes in renewable energy solutions for wireless sensors, is marketing an insertable chip that converts body heat into electric energy. Read the full story at Mashable.