Transparent Viewport?

Whilst getting all excited about the new PDF and SVG tools, it occurred to me that if Rhino had an option to make a viewport background transparent (i.e. not there at all, so that you can see your desktop through it) it could open up all sorts of interesting possibilities. Make Rhino “always on top” and you could reach through the viewport to whatever lies beneath, to manipulate a PDF or web page (or ?) to get it lined up with geometry in the Rhino model, and use it in much the same way as a background bitmap. Or, have another Rhino file open behind it and literally be able to ‘pull’ things through from one model into the other. I can see it might have to be restricted to only working on ortho viewports - it might become a bit brain-numbing in perspective…

I use a very old freeware to make windows semi-transparent. You can give it a try.
http://chime.tv/products/glass2k.shtml