FAST's wireless, dual sensor technology measures your engines airfuel 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, airfuel meter. The FAST Wireless AirFuel Meter uses an underhood mounted Bluetooth module, connected to oxygen sensors in both of your engines exhaust outlets, giving you the full story on the state of your engines tune. With the FAST Wireless AirFuel Meter, you can read both wideband oxygen sensors individually, or average them together for super accurate readings of the engines true airfuel 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 AirFuel Meter App includes a simple, built - in data - logger that records up to two minutes of airfuel and rpm data. Fuel calibrations are pre - loaded for measuring Gasoline, all popular Ethanol blends, Methanol, Diesel and more. Advanced AppModule features include 0 - 5 volt output for external data - loggers and digital gauges, an rpm activated window switch and a lean airfuel ratio safety cut - off. Additionally, an innovative Anti - Theft feature has been incorporated that allows you to manually activatedeactivate a vehicle immobilizing relay. A simple way to protect your vehicle from theft With features unlike anything else on the market, its clear the FAST Wireless AirFuel Meter is the best choice for the serious engine tuner.