With
this and
this, you can make a cable that at least outputs to VGA. It's not a true VGA mod, but it does the job quite nicely. The great thing about it is that you don't have to mod your xbox for it to work. I do recommend using an external 5v supply. I just run it through old cell phone chargers.
As far as making it switch between vga and composite, I believe that has a monochrome composite output on it, but that's no fun. For something like the 360's standard cables, you'd need to wire in a switch or three to change the video select pins appropriately.
I could make one for you, but for a home system and the price I'd want, there are probably
better options *Note: I can't speak personally on the effectiveness of that device. If you want a good one, probably look for more than 2 minutes in google.*
This post has been edited by ttsgeb: Feb 27 2013, 08:05 AM