A new API from Google will give you a way to develop apps based on Google Analytics real-time data. This means you can show how many people are on the site and work out what they are reading - as it happens.

The information from Real Time Analytics has been available for use since 2011, and can be used to show information about the current performance of websites. The data provided shows how many active visitors are on a site, which pages they are looking at, where the visitors are located geographically, and what the source is of site traffic.

Now Google has announced an invitation to join the beta for the Real Time Reporting API, which will let you make queries about your real-time data and use the information returned.

The announcement of the API on the Analytics blog suggests that one of the obvious uses is to query the API for the top visited URLs to construct a top trending content widget with the number of active readers. Writing on the blog, Linus Chou, Kasem Marifet & Ozan Hafizogullari say sites could also display the active visitor count in real-time, adding “Seeing the number of visitors also viewing a piece of content has a number of subtle effects such as creating a sense of community and credibility.”

There’s an example here of an android app to display the number of active visitors on a pebble watch:

Wider uses might be to analyze which areas of your site are proving popular, or to alert you when visitor numbers rise or fall significantly.

The GA superProxy will also work with the real-time API and Google Charts API (gviz), so you can publish a query that users will be able to access without authentication. This means you can make the request client side so a widget can be written in JavaScript and added to a site.

The API is being released in a closed beta, and you can sign up for it using a form that asks you to describe the project for which you would like to use it.