Trackpoints are the Holy Grail in GPS forensics. They are the electronic breadcrumb trail that tells an investigator exactly where and when the device was in a specific location. With trackpoints, criminal acts can be pinpointed down to almost the exact second a crime was committed. Almost all GPS devices collect trackpoints but even without trackpoints, GPS devices still hold a significant amount of data. Waypoints and routes will show the location to which the user intended to navigate or has navigated and a timestamp when the location was put into the device. Hybrid devices that have been connected to a mobile phone will contain much of the same information that an investigator would find on a mobile phone: call logs, SMS messages, and contacts. These can prove very valuable, particularly when paired with a track log. The call logs and track logs allow an investigator to see what time a phone call was made and from what location.
Because some of these devices are USB mass storage devices, any type of file could be found. Pictures, videos, documents, password files, encrypted containers, anything that can be stored on a computer can be stored on a USB mass storage GPS device. Connected devices add the complexity of having online content associated with them. Web history like Google searches, white pages lookup, etc. can all be critical information when assembling details for an investigation.
From: Enhancing Investigations with GPS Evidence by Ben LeMere