Classic barometer that measures atmospheric pressure.
It features direct reading in mBar, mmHg or psi and includes a barometric altimeter.
It also has relative pressure and altitude measurement displaying calculated vertical speed or vertical acceleration.

NOTE: This app requires device with a pressure sensor. It uses pressure sensor data to give accurate and instant atmospheric pressure reading. This reading is also used to estimate altitude without using GPS. Note that the altitude measurement can be inaccurate, especially with an uncalibrated sensor or when the weather is changing.