This page is a very simple example of a Web Intents file picker client application. Web Intents is a framework for client-side service discovery and inter-application communication.
Services that can handle pick intents could be anything that the user has installed, including and not limited to an image gallery such as Picasa or Flickr. A client application might be an email client such as Gmail or Hotmail.
See Web Intents web siteClick here to register services