Use the Android default DownloadManager to download files in the background. It will open the system download list when you click on the notification.
var dmg = require("com.miga.downloadmanager");
var filename = url.substring(url.lastIndexOf('/') + 1);
var file = Ti.Filesystem.getFile(Ti.Filesystem.externalStorageDirectory, filename).nativePath;
dmg.startDownload({
url: url,
filename: file,
success: onDone,
title: "Download",
description: "Download " + filename
});
function onDone(){
alert("done");
}