How to apply heatmap for the touchpoints of objects on the shelf in an input video?

I have build a model that applies heatmap based on the motion in an input video. Basically I had an input video of a shopping center, where the heatmap was applied to check the footfall in that store.

The code is as follows,

import numpy as np
import cv2
import copy
from make_video import make_video
from progress.bar import Bar


def main():
    capture = cv2.VideoCapture('input3.mp4')
    background_subtractor = cv2.createBackgroundSubtractorMOG2()
    length = int(capture.get(cv2.CAP_PROP_FRAME_COUNT))

    bar = Bar('Processing Frames', max=length)

    first_iteration_indicator = 1
    for i in range(0, length):

        ret, frame = capture.read()

        # If first frame
        if first_iteration_indicator == 1:

            first_frame = copy.deepcopy(frame)
            height, width = frame.shape[:2]
            accum_image = np.zeros((height, width), np.uint8)
            first_iteration_indicator = 0
        else:

            filter = background_subtractor.apply(
                frame)  # remove the background
            cv2.imwrite('./frame.jpg', frame)
            cv2.imwrite('./diff-bkgnd-frame.jpg', filter)

            threshold = 2
            maxValue = 2
            ret, th1 = cv2.threshold(
                filter, threshold, maxValue, cv2.THRESH_BINARY)

            # add to the accumulated image
            accum_image = cv2.add(accum_image, th1)
            cv2.imwrite('./mask.jpg', accum_image)

            color_image_video = cv2.applyColorMap(
                accum_image, cv2.COLORMAP_HSV)

            video_frame = cv2.addWeighted(
                frame, 0.7, color_image_video, 0.7, 0)

            name = "./frames/frame%d.jpg" % i
            cv2.imwrite(name, video_frame)

            if cv2.waitKey(1) & 0xFF == ord('q'):
                break
        bar.next()

    bar.finish()

    make_video('./frames/', './output.avi')

    color_image = cv2.applyColorMap(accum_image, cv2.COLORMAP_BONE)
    result_overlay = cv2.addWeighted(first_frame, 0.7, color_image, 0.7, 0)

    # save the final heatmap
    cv2.imwrite('diff-overlay.jpg', result_overlay)

    # cleanup
    capture.release()
    cv2.destroyAllWindows()


if __name__ == '__main__':
    main()

Now I want to apply the same heatmap on the objects placed in the shelf based on the touchpoints the object gets. My idea to process this is, to use the same code, but make changes only in the part where we detect motion. That is, I am using the background subtractor in the above code to subtract frame 2 from frame 1 to detect any motion in the video. Likewise, I am not sure how to detect the touchpoints alone from the input video with many other motions in the video like people moving around. I am unaware how to process this, even after surfing each and every site I could. Can anyone please mention the method I can apply here to show heatmap analysis on the objects in the shelf based on the touchpoints, in an input video.