A device may include a housing, a light-permeable electrode, a computing device, and a display or other light-processing element. The display or other light-processing element may be positioned at least partly within the housing. The device components may be arranged to permit passage of light through the light-permeable electrode and relative to the light-processing element. The computing device may utilize electrical activity signal information from the light-permeable electrode to determine electrocardiogram (ECG) information or other information about the body of a user of the device. For example, the computing device may cause such ECG information to be projected through the light-permeable electrode by the display or other light-processing device and/or obtain additional information based on light received through the light-permeable electrode by the display or other light-processing device.
