I've just found out that there was a microbial fuel cell based charger developed. It can allow cell phones to draw their power from the dirt.
The device uses a conductive surface that is able to harness the free electrons that are created by soil microbes during their metabolic process.
Plans are to distribute the charging device in Sub-Saharan Africa, where many people have cell phones but lack power in their homes to charge them.
Discussion
Related Ideas