1. A method for autonomous calibration of a pulse-transit-time monitoring device for measurement of arterial blood pressure, the method comprising: measuring a pulse transit time of a circulatory feature between a proximal sensor position and a distal sensor position, the proximal and distal sensor positions disposed along a single arterial transit path on a human body; parameterizing a modeled quantitative relationship among a set of quantities, at least one of which quantities is a quantity distributed with distance along the transit path; performing a measurement so as to provide a plurality of quantities from among the set of quantities; and solving the plurality of quantities, on the basis of the modeled quantitative relationship, so as to obtain the arterial blood pressure as a function of the measured pulse transit time.