What do you have in mind Royce?
Two existing components should already help individuals develop an app helping develop something like this: TextToSpeech component to make your app speak and SpreechRecognizer, so the app can be controlled with vocal commands.
This is not a tutorial in helping the visually impaired but it could be adapted.: HOW TO: Program the native SpeechRecognizer for Continuous Dictation and to do things
Here are some resources to help you learn to use the AI2 tools. A very good way to learn App Inventor is to read the free Inventor's Manual here in the AI2 free online eBook http://www.appinventor.org/book2 ... the links are at the bottom of the Web page. The book 'teaches' users how to program with AI2 blocks.
There is a free programming course here http://www.appinventor.org/content/CourseInABox/Intro and the aia files for the projects in the book are here: http://www.appinventor.org/bookFiles
How to do a lot of basic things with App Inventor are described here: http://www.appinventor.org/content/howDoYou/eventHandling .
Also look here http://kio4.com/appinventor/index.htm and here http://www.imagnity.com/tutorial-index/ for more tutorials.
Learn about components http://ai2.appinventor.mit.edu/reference/components/
and visit the Library http://appinventor.mit.edu/explore/library Help>Library on the MENU
Share your ideas.