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, wherein the obtaining comprises: obtaining a plurality of windows from the video, wherein each of the windows includes a predetermined number of frames; determining at least one quantized colour value for one or more colour models, for each frame in the plurality of windows; and determining consistency of the video by performing consistency analysis for a predetermined number of determinant windows from the plurality of windows, based on the at least one quantized colour value of each frame, wherein the consistency analysis is performed, in response to obtaining the predetermined number of the determinant windows.