If you've ever tried doing your own silkscreening (more accurately, "screen printing"), you'll know what a hassle it is to do the first part of the process: Mixing the photo emulsion, applying it and exposing it. It's fraught with challenges like getting the proper consistency of the emulsion, the proper light and exposure time. Before you can even print one shirt, you mess up a lot of screens just figuring out how to make the stencil.
I started thinking about these cutting-edge printers that I've heard about. 3-D plastic printers (scroll down a couple of articles). A guy in Make magazine made a chocolate printer for decorating cakes, and presumably for making 3-D objects out of chocolate.
This wouldn't even be that complicated. It would just be a printer that is set up to make silkscreen stencils. No photo emulsion. It just prints some sort of (inexpensive) quick-drying liquid on the custom-sized screens. When it drys, you have a screen ready for printing.
Of course, it plugs right into your computer, so the step to go from design to application is instantaneous.
This would probably be an expensive product, but not super-expensive. Probably for the high-roller amateur or small-biz professionals.