OnStar gives Volt owners what they want: their data, in the cloud | Ars Technica You wade through a great deal of marketing to find out a great deal of data.
I am glad that voltstats is back up and running. Looking forward to some additional data being added. BTW, if you are interested in adding some of the OnStar/Volt functionality to a Prius you might want to check out this project. Open Vehicle Systems Started with the Tesla Roadster and now expanding to the Ampera (European Volt) and others.
Here is the current PiP version of OnStar/Voltstats. Welcome to Google Docs PiP Spreadsheet For the non-plugin Prius I think most are using Fuelly.