Barometer Plus app measures air pressure and altitude using the built-in barometric pressure sensor on your device. It only works on devices that contain a barometer, such as iPhone 6/6s/7/8/X (including Plus models), iPad Mini 4/Air 2/Pro or later. Barometer Plus can be used for virtually all your outdoor and indoor activities, such as climbing, trekking, hiking and even stair climbing. Because air pressure changes normally indicate a weather change, you can also use this app to monitor and predict short term weather variations.