Adam Weiss writes "A biosystems engineering professor has just announced a "ripeness sticker" for fruit. According to this AP article, grocers throw out thousands of bushels of fruit a year because it ripens too fast (1 bushel is about 9 U.S. gallons). Mark Riley's RediRipe stickers turn from white to blue as fruit ripens. The stickers react with ethylene gas, a chemical which is released as fruit or vegetables ripen. However the article says "there are still bugs to be worked out: The stickers do not change color to reflect an overripe or rotten piece of fruit. Also, not all fruit produces enough ethylene to be detected by the sticker.""