I just read that a letterpress simulator called LetterMpress is being developed. It will be released first for iPads. You'll place and arrange type on a press bed, lock the type, ink the type, and print. You can print your design or export to other applications.
Apparently the developer is trying to raise development funds through KickStarter. (I have no connection to this project; I just thought it looked interesting.)
More info and video demo: http://tinyurl.com/4tm2ke9

