Built-in sensors include: Air Pressure, Ambient Temperature, Barometric Pressure, Colorimeter, Conductivity, Dissolved Oxygen, GPS, Heart Rate, Light, pH, Relative Humidity, Thermocouple, Turbidity and two Universal Inputs.     Typical activities include: Skin temperature, pulse rates before and after activity, sweat production and photosynthesis, solid, liquid and gas phase changes and pH titration.