How about this projector?
Product blurb: Getting people to crowd over your iPhone to show them the cool video you took of the chance encounter with a ten-car pileup on the highway or a celebrity sighting can get really difficult. The screen is small, and upside-down video doesn't really convey the best atmosphere - everybody has to pile toward one side of the iPhone.
What if there's a way to project your videos onto the wall? What if there's a low-cost way to do that? A simple dongle that you plug into the dock connector of your phone, point to a nearby white wall, and turn the lights down for a community screening? This device is that.
You can even plug it into another device with an RCA cable, and it comes with a tripod for your iPhone so that you don't have to keep holding it up.
Have seen these on many websites ranging from $90+