I knew there had to be something out there...
Made by Suntour, so it's a properly designed bit of kit.
I think it only works on coaster hubs, otherwise I'd buy one myself.
PS: What does this mean?
"the unit will freewheel in both directions to eliminate back pedal in the freewheel mode
Can you do fakies/ roll-outs in free-wheel mode without the need to back-pedal? Sounds excellent.