1. A method for monitoring a physiological parameter associated with a subject using a hand held device, the method comprising: obtaining, by a processor, a plurality of sample photoplethysmographic (PPG) features associated with a sample subject, from a video of a body part of the sample subject; selecting, by the processor, from among the plurality of sample PPG features, at least one relevant sample PPG feature associated with the physiological parameter, based on a ground truth value of the physiological parameter for the sample subject; and determining, by the processor, based on the at least one relevant sample PPG feature and the ground truth value of the physiological parameter, a mathematical model indicative of a correlation between the at least one relevant sample PPG feature and the physiological parameter, wherein the mathematical model is deployed for monitoring the physiological parameter in real time.