I got the idea when I was learning to cross a wide street with a white cane. three lanes in each direction - and it proved to be a challenge because I would veer left or right and frequently get confused and lost. Then I thought a compass would be helpful, but a quick survey of compass apps on iOS showed that they are either visual, or show your heading as a number that can be read by VoiceOver, but it is still not very practical. So I thought that I need to encode heading as something that my brain can easily decipher during crossing the street. I have prior musical training, so that's why I decided to encode heading as a musical interval. This allows my app to communicate with about 10 degrees precision and in practice this is well enough to go on a straight line for long enough to cross the street.
I see someones cane get hit by a car one time causing him to lose orientation and make an almost 90 degree turn in the middle of the road. If the cane is pointed towards or away from traffic people don't even stop anymore.
This was actually long ago but it stuck with me. Just now I realized what perfect analogy for life it is. You move towards something, something interrupts the journey and then you just continue, thinking you are moving in the same direction.
