All smart phones typically have built in accessibility features and functions, which provide a platform on which applications (apps) can be built.
If you develop an app for the public, the content and interface options provided should follow the best practice guidelines developed by World Wide Web Consortium (W3C). These include:
World Wide Web Consortium (W3C) provides ‘ ‘ Mobile Web Application Best Practice Guide ’
For information on making iPhone applications accessible, see Accessibility Programming Guide for iOS
For information on making Android applications accessible, see Making Apps More Accessible
For more information on testing for accessibility, see Testing Your App’s Accessibility
Mobile Web Content and Apps Checklist