An apparatus for detecting a physiological parameter of a user, the apparatus comprising: a housing comprising an optical sensor , a contact surface of the housing configured for placement proximate a targeted area of a user's body; a strap for securing the housing to the targeted area, the optical sensor comprising a light source and an optical detector , at least a portion of the optical sensor configured for placement proximate the contact surface ; and at least one optical barrier positioned between the light source and the optical detector , the at least one optical barrier comprising a laterally extending leg and a vertically extending leg, the laterally extending leg being positioned between the light source and the optical detector , the vertically extending leg being substantially perpendicular with respect to the laterally extending leg and extending from the laterally extending leg to a contact portion, the contact surface of the housing comprising the contact portion of the at least one optical barrier , wherein, the light source comprises a light source element and a light source lens , and the optical detector comprises an optical detector element and an optical detector lens , the light source lens is placed in closer proximity to the target area of the user's body than the light source element is, and the optical detector lens is placed in closer proximity to the target area of the user's body than the optical detector element is, the light source element is at least partially received by the light source lens , and the optical detector element is at least partially received by the optical detector lens , radially-inner edges of the light source lens are separated from radially-outer edges of the optical detector lens by the vertically extending leg of the optical barrier , and radially-inner edges of the light source element are separated from radially-outer edges of the optical detector element by the laterally extending leg of the optical barrier . a housing comprising an optical sensor , a contact surface of the housing configured for placement proximate a targeted area of a user's body; a strap for securing the housing to the targeted area, the optical sensor comprising a light source and an optical detector , at least a portion of the optical sensor configured for placement proximate the contact surface ; and at least one optical barrier positioned between the light source and the optical detector , the at least one optical barrier comprising a laterally extending leg and a vertically extending leg, the laterally extending leg being positioned between the light source and the optical detector , the vertically extending leg being substantially perpendicular with respect to the laterally extending leg and extending from the laterally extending leg to a contact portion, the contact surface of the housing comprising the contact portion of the at least one optical barrier , wherein, the light source comprises a light source element and a light source lens , and the optical detector comprises an optical detector element and an optical detector lens , the light source lens is placed in closer proximity to the target area of the user's body than the light source element is, and the optical detector lens is placed in closer proximity to the target area of the user's body than the optical detector element is, the light source element is at least partially received by the light source lens , and the optical detector element is at least partially received by the optical detector lens , radially-inner edges of the light source lens are separated from radially-outer edges of the optical detector lens by the vertically extending leg of the optical barrier , and radially-inner edges of the light source element are separated from radially-outer edges of the optical detector element by the laterally extending leg of the optical barrier . <EOS>