Marketed as a tool to improve the user’s focus, reaction time, and ability to learn new skills, the Foc.us headset uses technology known as transcranial direct current stimulation (tDCS). In other words, headset electrodes attach to the user’s forehead and pump between 0.8 and 2.0 milliamps of current into the prefrontal cortex of the brain. Available for $249, the headset also comes with an app that allows the user to control the headset from an Apple device.