There are projector accessories that project a super-wide image (cinema-scope adapters or something). I forgot what it is but it displays the entire 2.39:1 image with no bars and no scaling. However this a TV and would suit more people.
I also agree that this would really only be ideal with a movie-only setup. Since 16:9 != 21:9, Presto is right to assume for all intents and purposes that there will be scaling.
Nonetheless, I can't imagine watching a full 2.39:1 movie sans letterboxing at home on a big screen with no scaling.