BEP-0012 extends BitTorrent to support multiple trackers. Most BitTorrent clients use PEX to gather peers in addition to trackers and DHT. Various jurisdictions have pursued legal action against websites that host BitTorrent trackers. Snipe hunters therefore needed to be stealthy in addition to being good trackers and marksmen. There has been much controversy over the use of BitTorrent trackers. Glooko automatically pulls in data from popular fitness trackers and biometric devices. Oink's Pink Palace and What.cd are examples of private trackers which have been shut down. Fossil and Veracity both include distributed bug trackers. There are several common implementations of dual axis trackers. The panels on standard photovoltaic trackers gather both the available direct and diffuse light. There are several common implementations of single axis trackers. Alternatively they may be for specialized purposes such as fitness trackers. The company designs and manufactures headphones and wearable activity trackers. New eye trackers, such as the Tobii X2, allow for true plug and play capability. There are collar-mounted activity trackers for dogs.