The PDA (Personal Digital Assistant) is a device used by Rico which functions as the in-game options menu. It can be used to call in an extraction or heavy drop in times of need, shows statistics, and provides a detailed map with location markers, race markers, mission trigger points and other items of interest. Map legend.
It can be taken apart and bugged in under a minute, while the device is at the same time downloading info. This is evident at the end of the mission Casino Bust when Karl Blaine asks Rico for his PDA to add info about the faction leaders. Blaine enters his mansion, downloads the info onto the PDA's memory card and gives it back to Rico within a minute.
It can wirelessly download info from laptops as seen during mutliple faction missions, like Mile High Club, Siphoning Gas, Clear Skies and possibly more.
All Panauan faction leaders are aware, but not amazed by the PDAs abilities, which means that the Personal Digital Assistant is a pretty common device in the fictional Just Cause universe. Possibly similarly to "smartphones" in reality.
The JC2 variant of the PDA has a 3D map. This can be seen when looking at the mountains and moving east to west, or north to south.
Unrealistically, the PDA still functions after the EMP on Hantu Island destroys a boat or plane that Rico was using. In a real situation, the PDA would be completely useless and worth nothing.