If you want video on app start up. It won’t play on app turn off.
Now for video on key turn instead. Use the same triggers and actions as mentioned but 2 issues. One your video will play but it’ll stay on the screen so if it’s full screen it won’t show what’s behind it. You’ll have to add a fade in and out action.
Secondly you’d need to decide input for it reading. Using voltage would be my suggestion. Once battery voltage is above 0 play video gauge and fade out at same time. When battery voltage equals zero again fade in and play