FYI I just tried this with a pdf and it did not work, I got an error message on my kindle that says:
" Web Browswer cannot download this kind of file. Only files with the extension .azw, .prc, .mobi, or .txt can be downloaded to your Kindle."
@DiapDealer
If I wanted to make the .htaccess file cover all the bases would this work or should the application be different for the other formats (ie the x-mobipocket-ebook part)
Code:
AddType application/x-mobipocket-ebook .mobi
AddType application/x-mobipocket-ebook .azw
AddType application/x-mobipocket-ebook .prc
AddType application/x-mobipocket-ebook .txt
@Amalthia
I'm not sure if the type portion of the mimetype would be the same for another type of reader. Also since this thread is just for Kindle I'm not sure if this is the right place to pose your question

I'd wait until a reader like the one you're talking about comes out and then determine how to get it to work, I think it would depend heavily on the device itself.