A reflectance-based optical measurement device and a method for a reflectance-based optical measurement are provided. The device comprises an illumination and detection assembly configured to output light to a surface portion of a user for measurement and to detect the output light reflected from said surface portion of the user as a signal; a coupling member configured for coupling in a cableless configuration to a personal mobile processing device; a measurement surface configured to allow access to said measurement surface by the surface portion of the user; wherein said access is provided by the optical device being holderless such that the surface portion of the user is allowed access to said measurement surface from all directions in a single plane; and further wherein said coupling member is arranged to transmit the detected signal to the personal mobile processing device.