Originally Posted by DiabloScott

Or maybe you mean a lever-drive crank? This was a really old idea:



Here's another "de-coupled" crank - some videos on the site too:
http://www.powercranks.com/index.html

How do PowerCranks work?

PowerCranks are a patented training device that integrates a one-way clutch in each crank-arm. Each crank-arm will drive the chain but not each other. Imagine doing one-legged drills all the time, with each leg working independently from the other.