alloy.js

// For iOS7 only, set the window's top to 20 so they start under the status bar.
Alloy.Globals.windowTop = (OS_IOS && parseInt(Ti.Platform.version[0], 10) >= 7) ? 20 : 0;

// Optionally set the backgroundColor or backgroundImage to show behind the statusbar.
// Please note that the backgroundImage will cover the full screen, but only top 20px is visible.
// Ti.UI.backgroundColor = '#555';
// Ti.UI.backgroundImage = 'statusBar_bg.png';

app.tss

"Window[platform=ios]": {
    top: Alloy.Globals.windowTop,

    // The only place in 3.1.3 where you can set the statusBarStyle.
    // Leave out or set to DEFAULT for black instead of white text.
    statusBarStyle: Titanium.UI.iPhone.StatusBar.TRANSLUCENT_BLACK
}