Just working on my 1st sencha touch app and i'm having problems with finding information on the best approach for the app icon. After doing some research it seems the best approach for ipad iphone iphone 4 icons is to produce multiple versions 57px square for the iPhone 3G and 3GS, 72px for the iPad, and 114px for the iPhone4. Looking at the documentation for sencha touch I found the following :

    icon: 'icon.png',
    glossOnIcon: false,
    tabletStartupScreen: 'tablet_startup.png',
    phoneStartupScreen: 'phone_startup.png',
How does this work for multiple icons sizes bear in mind the iphone and iphone 4 having different sizing