If you want a secondary screen but can’t quite fit one onto your desk, you might want to check out ASRock’s latest invention — a PC side panel display.
Large and bright enough to serve as a proper monitor, this is certainly a fun gadget. Unfortunately, many of us won’t be able to use it.

PC owners have all that space on their chassis, and nothing to do with it. As long as you’re willing to give up being able to easily peer inside the case (and admire the RGB light show, if that’s your thing), you might like ASRock’s 13.3-inch Side Panel Kit. This is essentially a monitor, similar to that in a laptop, that is attached to the inside of your case.
As the panel is installed within the chassis, your case needs to have a side panel made of transparent tempered glass. It has to be sturdy enough to hold the screen, but it also needs to be see-through so that you can see it in the first place.
For a little side monitor, the IPS display sounds decent. It measures 13.3 inches, has a 16:9 aspect ratio, 1080p resolution, and a basic 60Hz refresh rate.