Be My Eyes is an iPhone app that connects visually-impaired people with volunteer helpers from around the world.
Visually-impaired people use the camera on their mobile device to shoot live video of whatever it is they need help distinguishing or reading. The challenge could be anything from knowing the expiry date on milk to navigating new surroundings. Sighted volunteer helpers receive a notification for help and a video connection is established. From the live video the volunteer can help the visually-impaired person solve their problem.
The app is open source, which means the source code has been made freely available and may be redistributed and modified.
Incredibly useful and very nicely delivered.