VizWiz is an iPhone app that allows blind users to receive quick answers to questions about their surroundings. VizWiz combines automatic image processing, anonymous web workers, and members of the user's social network in order to collect fast and accurate answers to their questions.
Since mid-2011, VizWiz has been used by more than 5000 blind iPhone users to answer over 50,000 questions. Most questions were answered in a minute or less, and all for free.
Check out this great VizWiz tutorial video created by folks at the University of Maryland Baltimore County: