Cool idea, with a little work this could be a very useful tool for color seeing folk. The method you use could definitely use tweaking though, Ive seen other sites that do this which produce images that look identical to the original to me (im red/green colorblind), but with this there is a significant difference.
The method is definitely lossy - it should be off but consistently off. i.e. the mapping is not perfect but if two colors look close to each other in our lossy mapping then they'll be close to each other in the perfect version. I'll probably update it soon anyway.
there are a few apps out there that simulate different types of colorblindness that I find useful for testing all sorts of things (websites, apps, videos and more) when I can't easily find someone who is colorblind. you might find them useful for testing, like http://colororacle.cartography.ch/ which looks to be cross-platform (I only know of ones for OS X).
also in terms of general feedback, I love the idea and it's great for occasional use for a small set of pages, but I can't imagine using the current feature set for any significant testing and testing of anything that's not a webpage. i really love the idea of delivering the whole screen, especially without installing much beyond a firefox extension :)
