I bought a used Kestrel 2500 off Ebay a year or so ago.
https://kestrelinstruments.com/kestrel-2500-pocket-weather-meter
That device measures barometric pressure, altitude, air temp, wind speed, etc. It’s a pocket sized weather station! I got it as I was always curious how hard the wind was blowing and what the temperature was on many of the Colorado summits I’ve activated.
It also serves as a backup navigation device which tells me the approximate altitude in the event my other electronic tool fails (I also carry a paper map and compass). It measures altitude based on barometric pressure so I need to remember to calibrate it at a known elevation (usually the trailhead). I seem to forget to do that a lot ;-).
73, Brad
WA6MM