Since Android has evolved I thought this thread could use some updating. I currently use:
Celeste Lite (free) - Sun tracker
DMX-DIP (free) - DMX to DIP calculator
FilmCalculator ($40)- Calculates just about everything to do with film. DOP, lense angle, sun, footcandles depending on actual instrument, focal length, lens matching, etc...
Bubble Level (free) - just as name says
Mileage (free) - logs and charts a history of all your business driving.
I have also found various other DMX tools but havn't implemented them into my work flow.