Feeling a little under pressure? Your iPhone can measure that.
Since Apple introduced the iPhone 6 and 6 Plus in 2014, most iPhones have included a built-in barometer. The first-generation iPhone SE didn't get the memo, apparently, and is an exception. Apple explained its inclusion as a means of determining relative elevation changes. Without diving too deeply into atmospheric science, iPhones with barometers detect your elevation based on current barometric pressure. The higher up you travel, the lower the pressure, which your iPhone translates into an approximate elevation reading.
Barometric pressure is essentially the force exerted by the air above you. Air molecules have mass, and the more air above you, the more pressure is exerted on you. It's useful information for determining elevation, but to be clear, barometric pressure also changes with the weather. By itself, the sensor can't tell if falling pressure means you're scrambling up a mountain or if storm clouds are rolling in. Apps have to depend on more information, like GPS altitude and local weather station data.
While your phone has all that data to play with, it's not immediately clear how you, as the owner, can take advantage of it.
A standalone app was never the purpose of including the barometer in the first place, nor is that the case today.
