Many of us in developed countries find it annoying when somebody calls and hangs up before you can answer. But in developing countries, "missed calls" are becoming an extremely cost-effective cue for transmitting and obtaining information—without incurring fees for voice calls or text messages. In India, for example, small businesses call vendors and hang up to indicate they need deliveries, fishermen use a "missed call" to inform buyers they are on the way back … [Read more...]