1. A method for determining blood pressure for a subject using a sphygmomanometer having a cuff and a pressure sensor integrated therein, comprising: measuring an oscillometric cuff pressure waveform of the subject using the sphygmomanometer, where the oscillometric cuff pressure waveform indicates the time evolution of the pressure inside the cuff during inflation and deflation of the cuff; representing the measured waveform with a physical model, where the model accounts for a nonlinear relationship between a cross-sectional area of an artery and blood pressure; determining unknowns of the physical model using the measured oscillometric cuff pressure waveform; and determining blood pressure for the subject using the determined model.