This armband is an early prototype of a wearable that responds to biometric data to help the user stay in an focused and relaxed state of mind. It consists of a wireless, head-worn EEG sensor, and an armband with a mounted LED matrix that displays a large block of color on the user’s arm. By interpreting EEG sensor data in real-time, the system can interpret the mental state of the user and proactively use color changes to help promote relaxation, focus and creativity. These color changes are perceived peripherally by the user. The intention of this prototype was to embody how a user’s behavioral response to a wearable also affects the system, creating an interplay of feedback that could be further studied in realtime reactive systems.