re: That's funny. However, wristwatches were a reality.
That doesn't make sense. For a sundial to be useful, you need to know which direction South is. But if you know already know where South is, you don't need a sundial. Any shadow-casting vertical object will do the job.
When a sundial was set up in a garden or ancient observatory, care was taken to align it to the compass directions, and anyone passing by to use it would have known that, and trusted it was properly aligned. Carrying one around with you would have been pointless.
There is a way to determine Local Apparent Noon with a sextant, or with any shadow-casting vertical object, even if you don't know the compass directions, but it won't help you with the other times of day.