Pound a nail into your monitor and rotate?
Seriously, you would make a sprite or a plain (depending on which works for your purposes). Then texture the screen with a bitmap that is a "copy" of your screen. A lot of exactly how you do this depends on what you want to achieve.
The same concept can be applied for blurring the entire screen. There is a Blur function, but it's really slow. An alternative is simply using the Get Image function;
Quote: "GET IMAGE Image Number, Left, Top, Right, Bottom, Texture Flag"
and set the Texture Flag to 0. Then paste them image and copy it again. Each time will blur the image more. You can also paste the image to a smaller bitmap to blur it even more.
"Droids don't rip your arms off when they lose." -H. Solo
REALITY II