In an embodiment of the disclosed technology, a bracelet is generally formed of a circular wire band that is elastically deformable. The system may select two segments of the physiological signal, shifted in time relative to one another by a lag value, and determine a correlation value between the two segments. An optical device is secured to the ceramic waferboard in contact with the alignment feature to thereby position the optical device. The airbag, when deployed, is adapted to from a cushion between the roof surface and occupants of the vehicle.