Radio frequency identification (RFID) tags are the front-runner for replacing bar codes in grocery stores. The little tags can transmit an electronic product code to a wireless receiver, speeding up scanning, and making the inventory process almost automatic. They still need to work out a standard method of communication and bring the cost down from 50 cents to 5 cents per tag, but the Auto-ID Center researchers believe that is possible by 2005. The technology was developed by a joint team from MIT and Cambridge University (bridging the ocean that separates the two Cambridges). Radio tags are already used in many applications, including library security (low frequency) and toll-collection (high frequency). When they become standard for tracking all sorts of products, perhaps they will also help you find your keys.