Linear Technology lists the LTC3108, an Ultralow Voltage Step-Up Converter and Power Manager than runs with an input of just 20mV producing a 5V output to power things such as low power wireless devices and processors. Surely there must be an application for such a device in ultra-QRP portable equipment? Imagine, where can you find 20-500mV of noise from? 50Hz crud in the ground, a thermo electric sensor, solar cells etc. I wonder who will be the first person to make a QRPp uW beacon powered using the 50/60Hz buzz available between a couple of earth electrodes in the ground?