I participated in a hackathon a few years ago. The task was to create a finance app using the first Pebble (remember: three (or four?) buttons, black/white no-touch display).

We thought hard about an actually useful finance app on this very limited smart watch, discarding any accounting or similar beacause input using three buttons is too cumbersome if you have a mobile phone in your pocket a few inches away.

We ended up creating a watch app that showed you the route to the next ATM on a map, along with a description of the route. Technically pretty challenging since we had to generate map tiles on a remote server and load them onto the watch. Also, each image had to be sent in two chunks since the transfer buffer was smaller than the screen...

Another group just assumed the Pebble had a camera, color display and a microphone and had no demo, just a power point presentation. They ended up as winners...