Microvision's SHOWWX+ Laser Pico Projector is a portable projector that can display up to 100". This can hook up to your laptop, iPhone, iPod Touch, iPad, and basically anything with TV-out. The projector uses lasers and not lights so there won't be any bulbs burning out or anything like that. It holds up to a 2 hour charge, so you can watch a movie when you are mobile. Now these things are a bit pricey, starting out at $299, but they do display a nice image and never need to focus. Imaging creating a case for this thing for the back of your iPhone or iPad. You would have a projector right on your iDevice. Anyways, that is just wishful thinking, Check out the ShowWX+ below!
SHOWWX+â„¢ Laser Pico Projector