It also said that SF wanted to introduce a demand based system for parking, which meant it would be a few cents if nobody needed the space and $6 if everyone wanted a space. Of course such a system wasn't realized.

Demand based parking meters exist in SF. They've been tested in various areas since 2011. They also have an app that helps you find parking using the same sensors that adjust the price.

See: http://sfpark.org/ or http://en.wikipedia.org/wiki/SFpark