I was looking for something in the iTunes store to address two needs I have for an upcoming photo trip. I want something that will provide me sunrise and sunset information and I also want to know the local tides. The first priority has been looking for sunrise/sunset apps.
I have looked at probably over a dozen apps by now, read some reviews, and even tested a few free versions. To me the leader of the pack is an application called Helios developed by Chemical Wedding. The app is aimed and film and still photographers and provides some really great information. In addition, it can work disconnected from a wireless network. That is important for me because I want to use it on an iPod touch 4G.
From reading through the online documentation the application will give you information about sunrise, sunset, angle of the sun, shadow length ratios to help you get an estimate of what shadows will look like at a certain hour.
Looks great, only down side is the price tag. It is running 29.99 USD. Quite pricing for an iPhone application. But, if it helps me plan and catch one good photo for my stock photo portfolio I can imagine it will pay for itself pretty quickly.