Thanks Mark - great responses and will need a bit more time to think through most of them - one thing I'd like to question is the point you made about the daily commute.
Data and feedback from our users says that they mostly use our driving theory test software on the sofa and in bed (along with on the loo). I am keen to really test the notion that putting educational content on mobile devices is about revising on buses and trains.
I have a post called
Handy Education not Mobile Learning (
http://blog.luziaresearch.com/mlearning/handy-education-not-mobile-learning) which says that putting educational content on mobile phones is more about convenience than it is about being mobile.
As you state that you use your iDevices daily, can you give some personal experience feedback about where you use them the most? Is it the commute or is it more mundane places - your desk, sofa and bed?