Eureka has found a disabled Kindle Touch feature which seems to be used in the latest Kindle Paperwhite model announced by Amazon (advertised as "Time to read"). He noticed that in
/opt/amazon/ebook/config/reader_plugins.xml there's a commented plugin called Reading Timer (located in
/opt/amazon/ebook/lib/ReadingTimer.jar).
Well, I uncommented the plugin and restarted the framework and ... It seems to work.
When you open a book, in the menu you find a new item "Activate reading timer" (already localized in IT, DE, FR, ES, ...).
After a first phase of "training" the timer begins to work. It gives (on the status bar) a projection of how much you have already read and how much you miss to the end of the book even if I don't know how accurate it is.
The initial training can be reset by removing the reading preferences file (warning: also font and margin preferences are reset, and the introductory page teaching how to turn pages is shown again once).
You can tap on the status line ad the bottom of the display to switch between different infos (time elapsed since beginning, time to the end of the section and of the book).
For more screenshots see
here.