I'm just old enough to remember when we wore actual watches, but not quite old enough to get why Douglas Adams was obsessed with digital watches.
But what I remember is that there was always someone else who asked "What time is it?" and you showed them your watch. And, of course, people who said "nice watch, can I see it?"
So: What I'd want is an app that makes me money every time someone else makes use of my device. Either via a direct micro payment, or: the app could put the time display over an ad, so I could get an ad impression based on the time they spend staring at my clock.
Maybe it could be developed alongside a cell phone app that lets people with phones request someone with smart watch to come give them the time? Of course, established cell phone app developers would complain it was infringing on their market... But, ... progress...
Ooh - and maybe an tBackup app: if your watch isn't working properly (i.e. it doesn't know what time it is), it will direct you towards the nearest person with a working watch!
Lastly, I'd want an "icebreaker" app. You've gone to a party, and according to your watch you arrived on time. However, half an hour in, nobody is talking to you or coming over to look at your watch. So you tap the icebreaker app, which figures out who is nearby to you, finds a subject that would be of interest to everyone around you, and presents you with an ad you can use to break the ice, and get paid page impressions based on the number of people in the room!