write an app in UNITY that recognizes human foot and a coin

first you must establish what kind of recognition technology should be used with UNITY 2017 in order to recognize a human foot and money coin. then write an app in unity for a smartphone that takes a camera picture and recognizes a human foot from a point of view from above view (and also side view) (see pictures attached) and money coin beside it. the result is the length of the foot the should be extracted from the knowledge of the coin's size.