Building Cross-platform Mobile Apps with Force.com and PhoneGap allows developers to leverage their existing web development skills to build mobile apps that can access Force.com data and APIs. PhoneGap is an open source framework that allows wrapping HTML, CSS, and JavaScript into native mobile applications. Developers can use libraries like forcetk to integrate Force.com functionality and jQuery Mobile or Backbone.js for UI development. The demo apps show how to build data-driven mobile apps that retrieve and display Force.com records on both iOS and Android with a single codebase.