I just received a set of the SkiA Sweetspot trainers from Nolo and fit them to my boots. They were recommended to me by another member (marznc) for balance and strengthening after knee surgery. Epicski has an article for the SkiA Sweetspot from last year. Since there is not a thread on these, I thought I'd make a placeholder for my experience with them and for anyone that has use these or other balance-point trainers.
The concept seems simple enough, and my hope is it helps me correct the over-pressuring of the front of my boots that has become a habit. At first glance, they seem to be like walking on Lego blocks. I'll give them a fair try.