BaroAltimeter!

iPhone 6, 6+, 7, 7+, or newer iOS device with a barometer only Use the iPhone 6 or newers ultra-sensitive barometer to calculate your altitude. Will find your nearest airport or allow you to enter your local airports IATA code to calibrate Perfect for VFR pilots as a secondary altimeter Currently only supports airports in the United States as well as typical USA units (pressure in inHg, altitude in feet)