Your iPhone or iPod touch or Apple Watch can now read the barometric pressure sensor built into all newer iPhone, iPad, and Apple Watch devices.

No internet connection is required to use this app, no data is transmitted. It just uses GPS, the barometric pressure sensor, and the new barometric pressure sensor built into the latest iPhone, iPad, and Apple Watch devices.

Please note, that a single barometric pressure reading is not enough to predict the current weather situation but the barometric pressure and its change over time is a very good indicator for weather changes.

The app allows you to monitor the pressure trends over the last 30 days as well as to predict upcoming weather changes by the change of pressure.

The app calculates the altitude based on GPS, so it can calculate any altitude anywhere.

It is not a scientific tool, it can not be used for accurate measurements, but is useful for calculating your altitude.

There are lots of apps that claim to be able to do this and many of them are very accurate, this one is not, but you can easily see the trend over time.