The only thing that comes close is the Hololens, and if you ever get a chance to play with one (which I do recommend!) you'll see immediately why it Isn't There Yet™. The biggest killer is that the field of view is tiny- think a single A1/Letter sized sheet of paper held at arm's length. It feels less like AR and more like a view portal, and since it currently has no way to block light behind its projections, everything is washed out. Not to mention that it's closer to the headset side of things than regular glasses.

It's certainly a start, but there's a long way to go.

Nitpick: you mean A4. As an aside to those who don’t get to use ISO A paper sizes, they are trés cool. The x/y edge sizes are the (edit) square root of two. A0 is 1 square metre in area. Each step (A1, A2, A3, ...) just chops the sheet in half.

Edit: https://www.cl.cam.ac.uk/~mgk25/iso-paper.html

Here's fun video about metric paper https://www.youtube.com/watch?v=pUF5esTscZI

As an aside, there are also ISO B and C series paper, although I believe that the C standard was withdrawn somewhat recently. The area of B_n is the geometric mean of that of A_n and A_{n-1}, while the area of C_n is the geometric mean of that of A_n and B_n. Without context, C4 paper sounds quite scary, until you realize it's probably related to A4 paper in some way. As to why it isn't just called A3.75, I have no idea.

Shoot, missed the edit window. Thanks for the heads up, though.