The details are sparse but it seems that Sunyang DNT has created a phone with a 12-inch heads-up-display. Now this could also be some sort of projector unit, which we have heard of before, or something else entirely. I suspect the HUD moniker is a misnomer.
What this seems to be, according to a TelecomsKorea post, is a projector that shoots an image of whatever is on the screen onto a wall by using a bright light and a transparent display. The possible uses could include video chat and standard business projector usage. An interesting, if odd, choice of display technology, to say the least.