We've been seeing continued improvement in the efficiency of thermoelectric generators, nanotech holds the potential for a breakthrough over conventional materials.
Something like this could be used at oil wells. Some wells burn the excess gas. This could be used to run the pumps in theory.
I used to have instructions from Popular Mechanics (Or Mechanics Illustrated) on how to make a thermocouple powered radio. The photo showed several arabs with one powered by their hookah.
Similar to the BioLite Stove which runs a combustion chamber fan and a USB charger off its waste heat.