Wikipedia
PressureNET is a crowd-sourced reporting network for barometric pressure data.
It works by having many users install it on cell phones that contain air pressure sensors (barometers) and GPS sensors. Once the location is known from the GPS data, it is able to send messages back to the server with the air pressure for that location on earth. With enough users running the application it is possible to create useful, global pressure data. It uses open source software running on Android phones, to collect data from locations around the world. The data is available on a public website.
With the announcement in September 2014 that the first apple device with a barometer (iPhone 6) was to be released, work started on an edition of the app for that platform
PressureNET cooperates with Sunshine for the iOS App . The Android App still exists.