@xpert,
In order to be sure that your redirect instruction is called when you just opened the app, you must wait for the Cordova Runtime Environment to be loaded and initialized by the app since the phoneui.showURL function uses ‘device’ variable that is being set by cordova on init, and docready happens before this. Please use next code to replace the phoneui.documentReadyHandler function:
phoneui.documentReadyHandler = function() {
document.addEventListener("deviceready", function() {
phoneui.showURL("http://google.com", "_self"); },
false);
}