It's like V-Ray RT or the interactive viewport in C4D.
You can use the physical renderer set to progressive and low QMC GI settings and you get a quick preview that's refining.
Here with scaled up interactive VP:
Does also work with corona. The downside is that you have to wait a few ms before the renderer starts again. pt/pt speed things up a bit.
But yeah, it's impressive. I saw the presentation and their goal of having 60fps while moving something etc. That would be nice +1
IPR!