Doesn’t Work on Apple Watch 5
Also, altitude units are only in meters, you can’t switch to feet.
Five star app of those could be fixed, but not usable now.

Archived App
This is an archived listing of the app previously available on the App Store.This app provides real-time altitude, atmospheric pressure, and effective oxygen percentage using your Apple Watch's GPS and barometer. Customize complications to display altitude relative to sea level or Mount Everest, or oxygen levels in a gauge. Pressure can be shown in various units.
2020.2.1
February 24, 2020
Altitude Watch is available for Apple Watch, iPhone, and iPod. It leverages the built-in sensors of the Apple Watch for its primary functionality.
The app uses the built-in GPS and Barometer on your Apple Watch to provide altitude and pressure information. Accuracy can be influenced by environmental factors and device sensor capabilities.
Altitude Watch supports multiple pressure units including PSI, mmHg, inHg, hPa, kPa, and Bars. You can customize the display to show your preferred unit.
Yes, you can customize the complications to display your current altitude in relation to Sea Level or Mount Everest, offering a contextual understanding of your elevation.
Altitude Watch has an age rating of 4+, making it suitable for a wide range of users.
The latest version of Altitude Watch was released on February 24, 2020, with the version number 2020.2.1.
The provided data does not indicate the presence of advertisements in Altitude Watch.
Altitude Watch is a paid application, priced at $2.99.