I need a couple of oaks for more bandwidth: The US Forest Service tracks weather with a network of automated stations; they are mounted on trees (the Service would like more of them) and generally solared power which often facilitates the need to clear trees to get to the sun. MIT researchers believe they can use the voltage difference between a tree and the ground to power the new ultralow-power sensors, eliminating the need for solar. The researchers think that the pH difference between tree and ground generates the voltage potential -- you get about 59 millivolts for every step in pH mismatch. They've even spunoff a company to capitalize on the finding -- Voltree Power.
Oddments: Tree power for networks