In the run up to the science GCSEs this year I have been using revision apps from the publisher CGP who make the revision guides we recommend to our students. I have to say that finding the apps was not straight forward as they only make them for iPhone, so a search on an ipad yielded no results. I then pressed the iPhone button and bingo! Dedicated apps for single and double sciences.
I have 6 iPads available and this boils down to about one between 4 in most classes.