Overlay apps like AVP has For Quest

Hello,

Are there any tutorials or doc on how you can create an app that just exists within a set Window like Apple Vision Supports?

I'd like to make a simple passive companion game (think pets) that can accompany you on the Quest in a small 3D window that can be with you while you are in other full screen apps like Horizon.

Are there any examples of this being done? Is it possible with the current Meta tech? Or is this only possible with AVP?