The technology relates to fabricating and employing a sensor unit with a malleable housing to obtain various bio-signals detected while the sensor unit is disposed in the wearer's ear canal. A set of sensor contacts is arranged along an exterior ear-contacting portion of the housing. The malleable material can be compressed for insertion into the ear canal, then automatically expanding to contact the ear canal at multiple points. The sensor contacts are distributed along the exterior of the housing to provide an orientation agnostic configuration. The sensor unit is able to be worn for hours, a day or longer. During wear, the contacts can detect EEG and/or MEG-related signal, such as Alpha waves. Other sensors may be included with the sensor unit to supplement the detection of bio-signals. The obtained signals may be processed on-board or transmitted to a remote device for off-board processing.