We are in the middle of the Perseids meteor shower over the next couple of days. This particular shower is made up of cosmic debris from Comet Swift-Tuttle. The peak nights should be tonight and tomorrow (August 11-12, 2014) , although there are always variables that can cause earlier or later peaks in the number of meteors per hour. There's a very bright moon in the sky over the next couple of nights making this an imperfect year for viewing this event, but with luck, you should be able to get some iPhone photos of the meteors hitting our atmosphere. You might try as soon as you can see stars and before the moon rises at about 9 PM local time, although the frequency of meteors will increase as it gets later and the moon rises higher.
The image above shows the long, arc-shaped trails of stars, but you'll notice other streaks that go at odd angles to the star trails. Those are either satellites reflecting light from the sun, or meteors burning up as they hit the earth's upper atmosphere. Take a long enough exposure and capture a lot of meteor trails in a photo, and they'll all appear to be coming from a certain area of the sky, known as the radiant point.
You could just aim your iPhone camera and hope to get lucky, but that's not likely to work very well. The best way to capture those meteors as they streak through the atmosphere is to use an app that lets you take long exposures. A tripod mount to keep the iPhone stationary is a good idea, or you can set your iPhone flat on a table or blanket that gives you a good overhead view of the sky. This shower is centered near the constellation of Perseus in the Northeast, so you could point your iPhone that direction, but meteors can appear anywhere in the sky.
One app that should work well for this purpose is NightCap Pro. This US$1.99 app has a variety of night shooting modes that will help you get that meteor shot. App creator Chris Wood suggests that you put your iPhone in Airplane Mode (Settings > Airplane Mode > On), then set NightCap Pro to Night Mode and then Light Trails Mode. Focusing on stars isn't easy, so pick something shadowed in the distance on the horizon to focus on and then lock the focus using the appropriate control in the app. Tap the shutter button and hope for the best. When you are done, tap the shutter button again to end the exposure. You can capture those dim photons for several minutes, but the longer the exposure, the more the moon will blot out the sky. You'll get better pictures away from city lights, but again, the moon will still be a bright distraction.
Other apps that can take time exposures are Shutter+ (free with in-app purchases), Light Camera (free with in-app purchases) and Slow Shutter Cam ($0.99).
The Perseids meteor shower is among the most reliable for watching those fast, bright streaks of light, but the next big one coming, the Orionids in October, will have only a sliver of moon so you can get another try if the Perseids don't work out well. There's a detailed list of yearly meteor events available from the American Meteor Society.