If they put a wysips on the screen then this will be unnecessary and any battery in the other half would just be gravy. You can see that company has already signed up some Chinese companies to use their see through solar panel underneath the screen.

Other options for a KB other half would be to have the keyboard characters painted with litroenergy paint or if that is too taboo for you you could just use their regular strong stuff to paint the characters (on top of a transparent plastic) and have the keyboard backlight come on for 1.5 minutes only before it turns off letting the characters glow themselves and have a kb shortcut to refresh the backlight to reenergize them if needed.

As far as small batteries are concerned the x-mini max 2 speakers that magnetically connect and collapse and expand to create fake bass last a very long time. They get very good reviews on battery life and each one is the size of a "now or later" candy. I see a flatter wider one in a other half as being totally adequate.

Related topics Solepower
and Scottevest