chrome/common/extensions/docs/examples/api/omnibox/simple-example/background.js

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// This event is fired each time the user updates the text in the omnibox,
// as long as the extension's keyword mode is still active.
chrome.omnibox.onInputChanged.addListener(
  function(text, suggest) {
    console.log('inputChanged: ' + text);
    suggest([
      {content: text + " one", description: "the first one"},
      {content: text + " number two", description: "the second entry"}
    ]);
  });

// This event is fired with the user accepts the input in the omnibox.
chrome.omnibox.onInputEntered.addListener(
  function(text) {
    console.log('inputEntered: ' + text);
    alert('You just typed "' + text + '"');
  });