Abstract: In one embodiment, a data processing method comprises obtaining one or more first photoplethysmography (PPG) signals based on one or more first light sources that are configured to emit light having a first light wavelength corresponding to a green light wavelength; obtaining one or more second PPG signals based on one or more second light sources that are configured to emit light having a second light wavelength corresponding to a red light wavelength, one or more of the first light sources and one or more of the second light sources being co-located; generating an estimated heart rate value based on one or more of the first PPG signals and the second PPG signals; and causing the estimated heart rate value to be displayed via a user interface on a client device.