I wrote a blogpost about the basics of accessibility in mobile applications. You can find it here
What to consider while delivering an accessible application
First of all, we have to recognise that accessibility should be a standard practice, not just a feature. According to iOS guidelines caring for accessibility means providing an extraordinary opportunity to deliver a superior mobile experience to every customer, including those with special needs. Well-designed applications are both more usable and more accessible, so designing for accessibility should be an inherent part of the design process. So let’s treat accessibility as “just the way we do things”. It’s not easy from the beginning, but it becomes addictive because of the great results it brings.
Read the whole blogpost here