1) Standard iPhone App icon in the following resolutions:
2) A UITabBarItem is required:
"The size of an tab bar image is typically 30 x 30 points. The alpha values in the source image are used to create the unselected and selected images—opaque values are ignored."
The above items will have the following specification:
72ppi, RGB, flattened, no transparency
24 bit PNG image file format
3) A favicon.ico is required.
All of the above are the single image scaled or converted to the appropriate format.
The image doesn't necessarily have to contain Brand text above.