Low power consumption computing is an interest of mine. While we have things plugged into AC that never really go off, they still consume a fairly high amount of power.
No, I'm talking about devices that never truly cut off. Or, at least, some portion of a device that never cuts off. How about a pico power AVR or MSP430 that runs off of a small coin cell battery for months/years. Running while quietly collecting data or waiting for a command from you to turn on it's host (we are still talking about parasitic computing here).
What useful things can we do actively under 1mA, while periodically sleeping at under 10uA?