RadarGolf is tagging golf balls with RFID chips.

The location-enhanced golf balls contain a radio frequency identification (RFID) tag. If the player looses it, he just has to point a handheld RFID reader in the general direction, and start walking. Once the ball is within the 40-100 foot range, the tag emits an electronic beacon. Then it becomes a hide-and-seek game of “hot/cold” with the scanner beeping faster the closer you get.

Found in The Feature.