Very small digital watches are available at almost no cost.
Today’s invention is a clip-on version of such a watch which is designed to attach discreetly to one’s spectacle lens and thus provide a readable indication of the time, just by glancing upwards and without having to wear a wristwatch.
It might be possible to exploit experimental psychology findings and place the watch display at the location in the visual field to which people naturally attend when thinking about ‘time’.