If anybody didn't see it, here's the PFF interview with Brandon Ally (co-founder of S2). It's nearly 40 minutes and fleshes out the testing process and how it's utilized by teams as another scouting element (along with 40 times, film study, etc.). As he says, it's not the Holy Grail, but can help match players with teams that are looking for something specific.
https://www.youtube.com/watch?v=_C4JT7T4pdY
One interesting point is that there about 16 "outfits" at the combine testing these guys, not just S2.