The iPhone has many capabilities and one of my favourites in photography is the ability to take long exposure photos. There are plenty of apps available to achieve this but the two that I gravitate to most are Slow Shutter Cam and Camera+.
Both are excellent for capturing a nice veil on a fast moving stream but where Camera+ trumps all is in its ability to capture a night scene with the ISO set as low as 0.01. You read that right. It goes extremely low which allows for beautiful night time images with virtually no noise.