Accidentally erased the original thread on this...
Are there ones that work like aircraft altimeters - bimetallic barometric systems for which you would set the instrument based on the altimeter setting at your closet airfield before you leave on your trip? If not, perhaps we should invent one?
The Avocet Vertech watch has a great altimeter. I use it mainly for cycling but am also a pilot and can tell you it's extremely accurate, tracking an aircraft altimeter perfectly.