The Vision Pro tracking is so good. I can leave a window in my office, go upstairs and still see exactly where I left it through the walls. Which brings me to a cool app idea:

A measuring app that not only allows you to leave measurements on flat surfaces, but also allows you to leave guidelines on walls to hang things straight.

But most importantly, the ability to set markers on the wall as a reference when drilling from the other side or wanting to run cables through walls.