I'm think on what used to be the flagship Fenix5/935 and newer that have barometers.
Everything can read the barometer, even watch faces on the older VA3.
But is there any chance there is an undocumented field that saves at least the start or ending reading?
If not, Garmin should consider adding that, especially in newer models that have the dynamic firstbeat vo2max that adjusts for altitude, etc.
Barometer pressure can be in millibars (mbar), inches of mercury (inHg), and millimeters of mercury (mmHg) so it's hard to know what to look for in the FIT, there also might be a scale or offset making it almost impossible to figure out unless Garmin voluntarily discloses it
One reason why I am curious is that if you know the air temperature, the air pressure, and the air relative humidtity, it is possible to figure out the amount of oxygen available in the air for a given altitude. There is no humidity sensor on Garmin watches (yet) but you can make assumptions with averages for an area at a time of year, so knowing the barometer pressure is gold.
