Tasker Video Player

This app will allow you to play full screen video on your device and specify the filename by writing a filename to a text file on the mnt/sdcard/video_file.txt in this file simply put the location of the video file you wish to play and when the app opens it will start playing fullscreen then close when the video stops.

I'm planning to put more controls like pause, current play position and stop, as unless your device is rooted force closing the app via tasker will not work.

Version 2 which will allow you to play the video in a floating window.

https://play.google.com/store/apps/details?id=com.mesh.digital.videoplayerv2&hl=en_GB