An on-body, particularly in-ear or on-ear, device, such as a headphone or an ear bud includes an electroencephalogram (EEG) electrode for measuring, monitoring and/or recording data indicative of EEG waves, or electrical activity in a brain, of a person wearing the device. The device can be configured to output data indicative of a baseline EEG comprising for example alpha, beta, gamma, and delta waves, which can be recorded and/or output on a display. Color can be designated as corresponding to certain activity of person wearing on-body device and for visual display color-coded EEG wave data could be summed so the screen color can change intensity and/or shade thereof representative information such as stress or relaxation level of personal wearing on-body device.
