The same logic that permits ordinary digital watches turns out to cover altimeters and thermometers too, as long as you don’t press to activate on Shabbat.
Q. Am I allowed to wear a watch with an altimeter and other prohibited touch-activated functions on Shabbat?
After a brief check on how those watches works, it seems that one must always activate the touch-sensitive glass by pressing a button or code. If so, it is just like most digital watches where, even though theoretically one may forget or accidentally activate electricity through pushing a button, nevertheless, we are not concerned or worried that one might do so. Since the “fall” of the Sanhedrin about 1900 years ago, we basically can’t issue new prohibitions, unless they are considered logical or necessary continuations of previously issued decrees, which isn’t the case in this situation (we have not heard mainstream poskim prohibit using such watches on Shabbat). Accordingly, the watch itself (without the electrically activated meters) is allowed unless one must electrically activate the watch to actually see the time. On the other hand, there are a few watches where even the time is not displayed until one presses a button, where it would accordingly, be prohibited on Shabbat.
With Love of Israel, Rav Ari Shvat
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