I've been working on a way to do accurate indoor "GPS" on the iPhone and iPad, just for the challenge of it really. However, since releasing the app I've begun to wonder if I could make it useful for vision impaired users.
The app, which is called "Indoor GPS", is not suitable for vision impaired users at the moment (it doesn't even do VoiceOver properly) so I'm not suggesting anyone tries it yet. But I'd be really interested to hear whether people think it has potential.
The underlying technology can track the device's movement in 2D (not up or down) to an accuracy of a couple of centimetres. Although the effect is like GPS, technically it is completely different - it uses the device's gyroscope and accelerometer.
The idea is that a vision impaired user could select a pre-recorded route from a list such as "Kitchen sink to front door". The device would then issue audio instructions such as "Right 90" meaning turn right 90 degrees, and "Forward 3" meaning take three steps forward. These instructions would be created on-the-fly depending on where the user has actually ended up, just like a car GPS does. So, for example, it's not dependent on the user turning exactly 90 degrees as it would ask them to turn a bit more or a bit less if necessary to keep them close to the pre-recorded route.
I know next-to-nothing about the needs of vision impaired users, so this may be of no use at all, but would welcome any feedback on the idea negative or positive.