I'd file the Cinemin Slice under the heading of Cool, but Limited. This dock for iOS devices contains a pico projector. Pop in your iPad, iPhone or iPod and the Slice will project video from the device as large as 60 inches diagonally across.
But for a one-trick pony, the Slice doesn't come cheap: $430. If you're really committed to using an iOS device for all your video needs, that may make sense. Otherwise, it might make sense to spend your money on a more versatile projector.
Here's a short video showing the Cinemin Slice in action.