The response of surface temperature to an increment of carbon dioxide is logarithmic.

FORBES: Global Warming Flatliners

Unlike almost all competitive products that use only one sensor to 'read' the body, BodyMedia's monitors incorporate temperature, heat flux, galvanic skin response and 3-axis accelerometer sensors to get accurate measurements of calorie burn, exercise intensity and sleep patterns that affect weight as well as health.

ENGADGET: BodyMedia's CORE 2 armband tracks your health, or lack thereof

That's caused by the adrenaline and stress hormones that the body releases in response to the shock of the cold temperature, but experts say that these rushes are not as healthy as people think.

CNN: Are polar bear plunges good for you?