Application
 

What are the applications you consider indispensable for an overlander?
Thank you

Assuming you are talking about smartphone apps


iOverlander of course. Still totally free
Mapping and navigation app of your choice. Mapsme seems universally popular - because it is free. osmAnd has a paid option and has lots of bells and whistles that for instance allow you to interact with Open Street Maps. Current favourite is Sygic which does cost a few dollars more but is much smoother than the others. Has the features that you need and not so much of the clutter that you don't need.
Currency converter updates online and usable offline
Google Translate - covers all the languages and many can be used fully offline.
Whatsapp and Skype
Prey or other phone finders
Unit converter app can be useful
Whatever financial apps you need for managing your affairs back home and on the road.
Country-specific apps for finding camping spots in certain countries where iOverlander has limited coverage - USA (Allstays), Europe (several) and Australia (wikicamps Australia

and of course about 100 more that you also couldn;t leave home without.

Could also consider a Garmin loaded with Open Street Maps for every country you plan to travel through as in many respects it is better than using a smart phone.