The Ottobed by Karim Rashid is a seriously space-saving piece of furniture. The bed actually folds away into a tiny little square that you could probably use as extra seating if you needed to.
The idea behind the Ottobed is that it combines the functions of an ottoman as well as a traditional mattress. The Ottobed is quite colorful, giving a pop of color to any room. I'm not entirely sure how comfortable the Ottobed would be, but coming with a pillow and a mattress of sorts, it can't be all that bad for a foldable bed.