You can make the battery life a bit better by turning off bits that you don't need (Bluetooth, wi-fi, sat nav), and reduce the frequency that your phone checks for email. And make sure that you terminate applications once you are finished with them, otherwise they just carry on running in the background, using up CPU time and battery power.
P.S. Dropbox gets my vote - it's brilliant if you are sharing census images and photos with other genealogists.