1. A method for self-aligning a sensor array with respect to blood vessel or other targeted area of a user, comprising: providing an optical sensor array, the optical sensor array comprising an array of discrete optical sensors arranged on a band, such that the optical sensor array straddles the blood vessel of a user, wherein each of the discrete optical sensors has a triangular configuration comprising a single photodetector surrounded by three light sources that emit light of a different wavelength that is detected by the single photodetector; performing, by a processor, a sensor calibration of the optical sensor array at periodic intervals during operation to determine which one of the discrete sensors has an optimum position over the blood vessel, the sensor calibration comprising: activating each of the discrete optical sensors to generate respective signals; designating as the optimal discrete sensor a particular discrete optical sensor producing a highest signal-to-noise ratio; and using the optimal sensor to collect physiological data of the user.