Human body could power smartphones, pacemakers and other devices
Does "other devices" include armies of malicious robots/AIs?
This isn't requiring us to eat more, it's just using the excess energy that's wasted.
I should think the sheer amount of energy wasted everywhere else in life, from my heatbox of a computer to my shitty car to my poorly insulated house, far surpasses the meager extra calories I could offer.
The only thing that would make sense to me is a kinetic-powered MP3 player because seriously my Zune has awful battery life and I run every weekday.