In many of the wealthier countries, obesity is an increasing problem. Low-quality food is cheaper than high-quality, and many of these low quality foods are full of empty calories, leading people who eat them to become overweight. The usual standards of diet and exercise are difficult for most overweight people, exercise because they have little spare time and are left tired, and diet because quality food is expensive and they miss their favorites after only a short time.
60% of the US population is overweight, and in wanting of an easy, inexpensive solution. And I might have it.
A device including a glucose converter is connected to the legs. (One device per leg, please.) The converted glucose produces electricity, which we can use to, say, power a microchip. The lowest powered device I know of, a 5 watt device, would burn an extra 103 calories per day. The highest powered device I know of, 300 watts, would be 6,190 calories per day, obviously too much. These calculations are based off the of patently unreasonable assumption that the device is 100% efficient, which it clearly won't be. So in practice, the device would use up more Calories than I listed here.
What would a microchip in your leg be able to do? I suppose it could, on a schedule, say 3am to 5am, twitch your leg muscles for extra energy use, or it could just track its own energy use, or the cycles could be used for a charity project, such as Folding at Home. The implantation clinic should have a number of software options for people who get the implant.
One potential pitfall is if the device makes the user hungrier. If it uses 103 calories per day, but makes the user eat an extra 200 calories per day, the user will get fatter. What connection does blood glucose level have with hunger?