Are you as annoyed as I am when you have to create the 7 (assuming you use Spotlight and Settings) different icon sizes that Apple requires iOS apps to provide? This post should be a real time-saver if you created your original icon in Photoshop.
One neat thing about implementing this auto-resize functionality as a Photoshop script (instead of a bash script using imagemagick and friends) is that the resize can take advantage of vector information (shapes, paths, layer effects) to provide a higher quality result than simple pixel downsampling can provide.
Open your original high-res icon. If you created your icon primarily out of shapes, paths, and layer effects then this technique will really shine!
From the Photoshop File menu select Scripts and then Browse.
Select my save-for-ios.jsx script that you downloaded in step 1.
Select the output directory for your resized results.
Select the prefix for your resized results. The final resized files will be named prefix29.png, email@example.com, etc.