This video is of Florent Soulas destroying everything in his path without the use of a chain. By taking the chain off he essentially gets a freecoaster hub (allowing one to be moving backwards without having their cranks move with the rear cog) without the cost of one. The drawback would be that you really don't have a conventional way of moving forward, unless you pump really aggressively (min 1:35-1:47). Which is pretty much what Soulas does during the video
0:32 180 to backwards manual to 180 forwards manual to 360 out
3:24 180 onto ledge to fakie turndown
Florent Soulas Chainless from adrien delaforcade on Vimeo.