Finished in an eggshell color and being slightly larger than a wristwatch, the BodyMedia CORE Armband is very minimalistic and unassuming. The device is secured to the upper arm by means of an elastic band with a Velcro closure for a tight fit. The monitoring unit is held but is easily released with a firm press. Doing so uncovers the mini USB connector for syncing to your computer and charging. The CORE Armband runs off of a lithium polymer battery that provides 4-6 days of constant monitoring, while the internal memory is limited to approximately 14 days of steady use. The battery level can be checked at any time by depressing a button on the top of the unit to activate a single LED. If the light's green, you're golden.
At first glance, you would never think the CORE Armband was a $150 piece of hardware, but a look at the sensor suite housed inside might change your opinion.Turning the monitoring unit over reveals a metallic panel with raised sensors that measure galvanic heat response, skin temperature, and heat flux. A 3-axis accelerometer rounds out the package. Broken down into terms that the average person can understand, these four sensors monitor calories burned, steps taken, and hours spent sleeping.
The electrical conductance of your skin varies with moisture level, and can be measured between two points along the surface of the skin by sending a small amount of current through the body. This conductance can vary by a few microsiemens, which can be sensed by a well-calibrated instrument. Because our sweat glands are controlled by the sympathetic nervous system, certain emotions can trigger galvanic skin responses. Lie detector's operate on this principle. Combining the GSR with skin surface temperature and heat dispersal readings enables the CORE Armband to accurately estimate your calorie burn in real rime. The 3-axis accelerometer inside the CORE Armband is no different from the one found in your smartphone. It can tell when you're standing up and moving about or lying down for a night's rest. For those of you who have a desk job, the CORE Armband might mistake your strenuous cubicle work for a sleep cycle, so we wouldn't recommend showing off your progress charts to your supervisor if you've been nodding off or skipping out of the office.