The Bluefly varios measure vertical speed and altitude based on atmospheric pressure. The pressure sensor inside the Bluefly does this 50 times every second, with a resolution that enables the measurement of tiny altitude differences of just 10 cm. Turn it on and it beeps pleasantly when you go up. It is super responsive.
Flight instruments are awesome devices to help pilots know the air. The best components are cheap and the instruments should be too. The BlueFlyVario project grew from a not-for-profit hobby that got out of control. The Bluefly varios of today remain focused on meeting what pilots need to fly. This pilot focused philosophy continues to motivate the production and ongoing development of awesome little varios.
Choose the Bluetooth_USB model to use as a stand alone vario or to connect to Android or iOS devices for use with flight apps, or the Bluetooth_GPS_IGC model if you need to send GPS data to your Android or iOS device and you want onboard IGC recording. Or choose the TTL_GPS model to solder to a Kobo or other device with a TTL Serial port for use with xcsoar.