I've been interested in this for a long while especially in memory models for forgetting patterns beyond simplistic SR expanding schedules.

We developed http://membean.com that utilizes some of this technology and we've been able to make this a successful business albeit in a restricted domain. But as others have pointed out .. it's hard to sell this. We've managed it because of stellar content built around our engine: http://membean.com/exemplars. Without excellent content it would have been hard to get this off the ground despite us able to show that we outperform existing SRS tools.

Most recently Smart.fm tried this and failed.