This device measuring electric current through the skin is related to a good amount of sweat from the body. Sweat gland activity depends on the sympathetic nervous system - control department of psychological reactions. There is something like feeling a chill run down spine, the conductivity of the skin will increase significantly.
Rosalind Picard and colleagues at the Laboratory of MIT Media Lab in Cambridge, Massachusetts has developed a wrist strap studying emotional state of autistic children - the children do not always say again with around the body about what they are feeling.

Many autistic children suffer from seizures, Picard said, and its consequences are very serious when the number of deaths per year even more than cases of breast cancer.
Brain wave activity will be blocked after going through convulsions. EEG can measure brain activity, but requires a lot of complex sensors are attached to the scalp, so we cannot carry it 24/24.
The new device is capable of receiving signals earlier than EEG because EEG can only operate in the cortex. The most obvious signs appear until 20 minutes before the seizure.
"If you suffer from epilepsy, was afraid you'd sleep at night," she said. "With the wrist strap this signal, you can know and call for help before the danger happens."