> Buy those Suunto wrist mounted compasses, altimeter and thermometer...and stick them on
> the watch band.

I had a wrist-mounted compass, but I found it too obtrusive. I kept knocking it. Now I have a Casio Sea pathfinder, which is solar-powered and has compass, barometer and thermometer.

The compass is better than nothing, and it does save me carrying a separate one on my keyring, but I don't really rate it. It can give misleading readings if I don't hold it level (which usually means taking it off my wrist).

The barometer is not as good as the one on my previous Casio because you have to press a button to see it. In practice it doesn't get used. Also, it has no altimeter (which suprised me).

I've never used the themometer. Normally it gives a reading somewhere between my body temperate and the room temperate, which is useless. The only survival use I can think of is if you have to sterilise water by heating and can't boil it.

I am undecided about the solar power. The power is of course stored in some kind of battery, so I doubt it will last forever. A good replacable battery watch might be better.

For my recent skiing holiday I left this watch behind and took my previous Casio instead. The older one is less bulky, has a better barometer, and also has an altimeter which could be more valuable in mountainous terrain.

I like having an objective measure of time. I should think it would be useful both for elapsed time (eg how many hours have I been walking?) and for absolute time (how long til dusk?). It can help plan and allocate resources, and coordinate with other people.

It is pretty much essential to have a watch with you for alpine skiing, because the lifts close at 4pm and missing that deadline could be the start of a bad night. The guidebooks say as much: each person in the group should have their own watch and piste map. Sometimes, a watch gives the first indication that you are in trouble.