Hi there,
I just watched the "Hand Crank Phone Charger" Episode from years ago where Ben tried to charge a cellphone by using his "walking energy". Unfortunately, that didn't work because the stick, taped to his leg didn't move the gear inside the flashlight at all.
Just like the instant can cooler, Ben could try to rebuild this one. Maybe by using a driving rod, that turns a linear movement into a circular movement. (I'm not quite sure if the translation is correct. In Germany we call it "Pleuelstange". Some other translations can be found here: http://www.dict.cc/?s=Pleuelstange )
Hoping to see that in a future episode 
