At just $14.95, this fruit powered clock isn't the most expensive holiday gift, but it is a pretty cool conversation piece. The idea stems from the idea that Alessandro Volta invented the battery based on experiments with lemon juice over 200 years ago.
Buy it at the Science eStore, which describes the clock as follows, "A digital clock and calendar powered by food! This fruit powered digital clock and calendar combines micro-electronic technology with the natural electrical potential of a fresh fruit or vegetable. The Fruit Clock uses the original scientific principles on which all modern electrical storage batteries are based. Just add a fresh orange, apple, lemon, lime, pear, banana, or any another convenient fruit or vegetable to the supplied components in this kit and you have the perfect synthesis of nature’s own electrical power resource and the accuracy of a digital clock."