Though it's not the only portable projector on the market, Brookstone's Pocket Projector for iPhone 4 seems to be one of the more elegant options for portable large-format viewing.
The slide-on docking case includes the projector unit, which makes setting up a presentation or video-viewing session quite easy when you're on the go. The 15-lumen LED lamp will give you a crisp 640x360-pixel native resolution that will stay clean up to 50 inches.
Of course, your surroundings play a major role in how crisp the picture quality is with any projector, but especially with the less powerful, portable models. You'll want to get your room as dark as possible to ensure the blackest blacks and best contrast ratio you can get.
The Pocket Projector also includes a speaker for audio and has a built-in rechargeable battery that can be recharged via USB cable. You can also use the projector as a battery backup case for your iPhone if you're running low on juice. Though the billing says that the Pocket Projector is for iPhone 4, it should also be compatible with iPhone 4S devices because their design is pretty much identical.
Having a projector case for your iPhone can be a great way to entertain your kids at a hotel room while traveling or a tech-savvy way to show a presentation in a business meeting. Together with Apple's Keynote (available on the App Store for $9.99 as a universal app) and iCloud (free to iOS device owners), you can easily create presentations and keep them backed up and ready to use on the go.
You can place your order for the Pocket Projector for iPhone 4 Devices over at Brookstone. The unit will cost you a cool $229.99 with service protection plans coming extra, and it ships the week of November 21.