I have always dreamt of electronics powered by the same stuff living organisms use as an energy source. Just imagine: your laptop/phone/whatever bleeps "I am hungry" and you, instead of desperately looking for a nearest wall socket to plug in a charger, open a little drawer at its side and slide a food pellet in. A lump of sugar is packed with energy and breaking it down produces only water and CO2, i.e. no solid waste to take care of.