The Register: "Canadian scientists have discovered how to generate electricity - by nothing more than pushing water through a fine glass tube.
As water passes through the tube, tiny amounts of glass - itself a supercooled liquid - 'dissolve' into the water. That gives the surface of the tube a positive charge, which attracts negative ions in the water. The flow of the water carries the positive ions onward, resulting in a net difference in charge between the two ends of the tube. That difference amounts to a voltage of around 10V. "
Between the water and the insects, we should have a pretty stable power source for small devices in the next decade or so.