Android development

Android Developer I required an android module which can have different functions. Simply by calling different functions I can get the data of the viewer count. For counting viewers we will use device front camera. It should support Kitkat, lollipop, marshmallow, nougat. Main purpose of developing this module is I want to track the numbers of viewers, count and identification. E.g. there is a small movie running on device and I want to track the number of viewers watching movie and how many viewed the movie when the movie ends. If anyone (viewer) stops watching that movie for some time and leaves before the movie ends, it should still remain as counted because that viewer has watched small part of movie. If the same viewer comes back before the movie ends and start watching that movie again then it should not be counted again because same viewer is already counted in first part. So it is important that users should be identified. So, if that movie is of 5mins for example then I will keep on calling the function after every 1min. And if in the first call I will get count as 5 viewers and after 2min I make another call and if any one of the viewer is gone and another new 2 viewer joined or added then I should get count 7. Now in 3 minute the viewer who left will come back and start watching movie again, then the count should remain the same that is 7. After 5mins I will call function to clear the count and the process will repeat with another movie and I will get new count for that movie. Also, it should be tracked from 8-15 meters distance.