FAST's Wireless dual sensor technology measures your engine's air/fuel ratio with precision accuracy all from the convenience of your smart phone! FAST has revolutionized the tuning industry with the most advanced App based wireless air/fuel meter. The FAST Wireless Air/Fuel Meter uses an underhood mounted Bluetooth module connected to oxygen sensors in both of your engine's exhaust outlets giving you the full story on the state of your engine's tune. With the FAST Wireless Air/Fuel Meter you can read both wideband oxygen sensors individually or average them together for super accurate readings of the engine's true air/fuel ratio. For engine tuners on a budget a single sensor version is also available. Easy to use with any iOS or Android device the FAST Wireless Air/Fuel Meter App includes a simple built-in data-logger that records up to two minutes of air/fuel and rpm data. Fuel calibrations are pre-loaded for measuring Gasoline all popular Ethanol blends Methanol Diesel and more. Advanced App/Module features include 0-5 volt output for external data-loggers and digital gauges an rpm activated window switch and a lean air/fuel ratio safety cut-off. Additionally an innovative Anti-Theft feature has been incorporated that allows you to manually activate/deactivate a vehicle immobilizing relay. A simple way to protect your vehicle from theft! With features unlike anything else on the market it's clear the FAST Wireless Air/Fuel Meter is the best choice for the serious engine tuner.