I would like to get a personal monitor (<22") where I can connect my Wii alongside my computer. However, I am unable to find any models which have the inputs available. All I need is something which will accept DVI-D for the computer and either composite or component for the Wii. But so far, every monitor I've looked up only has the basic DVI-D and D-sub ports for GPUs (apart from a 28" Viewsonic, though that's much too big).

At this rate, I am wondering if there are any specific converter devices which would allow me to input a composite/component signal and output it to a D-sub connector?

Barring all of this; would such a set up work? Would the monitor read whatever signal's active (ie. whether my computer or Wii is on) or would it be unable to distinguish between having 2 video signals plugged in?

It would work fine, any decent monitor will have a' button to switch between the different sources. I have a Dell Ultrasharp 2005FPW 20.1" Widescreen LCD I bought many years ago that has DVI, VGA, S-Video, and Composite inputs. It has a button that switches between these four sources. I have the DVI hooked up to my PC, the VGA hooked up to my Xbox 360 (using the Microsoft VGA HD cables for Xbox 360), the S-Video hooked up to my DirecTV Satellite Receiver box, and I do not use the composite.

I have a 20 inch acer monitor with a DVI and VGA port. I have the DVI connected to my pc and the VGA connected to my XBOX 360 (like Adam). However, my monitor does not have a button to switch between the two sources. I have to put my computer in stand-by (or power it off) to use the 360 without disconecting any cables.

Yeah, so make sure the monitor you buy has a way to switch between sources whether it be a button or on some monitors possibly an option in the menu.