How to make my app interact with Android home screen?

Question

I am building an app that uses frontal camera to track where user is looking at the screen. When user blinks, smartphone registers that as a tap. Currently it works "inside" my app. I have a few dots around the screen, when i look at one of them and blink, it changes color.

But how can I make it work on the home screen/with other apps? Say if user looked at the facebook app, blinked, it would open.

I was thinking of a pop up window like Skype. I could design it as a cursor and it would be displayed above the home screen and all apps. But if i would blink(tap) it would perform an action inside that popup/widget and not click "through" it.

Are there any codes that can make my app interact with other apps. Maybe Accessibility services?

There is a similar app that can create a mouse on the homescreen, when user waves his hand (no physical touch) it registers that as a tap. How can I recreate that?

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