Ephemeris: 1) calculations giving the path of astronomical objects across the sky. 2) a watchface that displays the path of the sun and moon across the sky. 
Select your location (lat/lon) in settings.  The sun and moon transit from local midnight (on the left) rising above the horizon, setting, then back to midnight.  
Features:
- All calculations are done in the pebble's small brain.
- Moonphase is computed and displayed.
- Solar / lunar elevation and azimuth can be displayed -- information changes each minute.
Issues:
- B/W display 
- Lunar display has problems in the tropics