It was Richard Mumford iirc, its called the 'Wrist Rocket' a small ascender (the same one he uses for the SAKA) with a wide webbing wrist strap closed with velcro.
I have one and its useful, but I want to replace the webbing/velcro wrist strap with broad, strong elastic so I can rapidly pull my hand out if something goes a bit 'Uh oh' .
The way its set up at the moment, your hand is pretty much trapped, and you'd need two hands to get out of the strap or disengage the cam.
I figure with a similar width of elastic, it would be enough to keep it on my wrist, yet not so tight I can't just pull my hand out through the elastic. Project in waiting.