The Nuvinci gear-hubs for bicycles are worse than usless, they can't handle more than 26 gear-inches of torque (with human legs). And they weigh 11lbs. The maximum torque before it starts slipping is 130Nm or 96 LbFT . One wheel revolution to one crank revolution is the lowest gear possible.
Some one said they saw a vidio of some guy jumping on the pedals, and thought that it showed how strong the thing is. All it really shows is that it takes much more leverage to move in higher gear. And it shows how strong the chain is; I have torn chain links just climbing hills in low gear.