Is there a way to do this without having to sudo on one or both ends?

You don't need to use sudo at all. I just tried it without, it worked fine. (On OpenBSD, but that shouldn't matter.) Logging doesn't have anything to do with sharing sessions, either, though it is quite useful for other stuff.

The multiuser section of the manual is here (http://www.delorie.com/gnu/docs/screen/screen_25.html), and there are a couple commands for changing user permissions.

You can login as the same user and use the same command (without sudo).

> Just sayin.

Not super-saiyan.

It works under X as well.

$ xrandr -o inverted

To get back to normal,

$ xrandr -o normal