Devices and method for accurately measuring the length of film feeding into a pre-stretch carriage from a supply roll and the length of film exiting after the pre-stretch carriage in order to accurately determine the actual percentage of film stretch occurring during the wrap cycle are provided. A first idler roller mounted on the frame of a pre-stretch carriage before the pre-stretching rollers and second idler roller mounted to the frame after the pre-stretching rollers are included. Optical rotary encoders are driven directly by idler roller shafts as stretch film passes around the shafts during film application. Systems including internet of things (HOT) devices can be fitted or retro fitted to a wide variety of stretch wrapping machines.