Purpose of device tracker is to show you where the agents were at the time of the interaction. To access this, go to Reports from the top menu and select 'Device Tracker'. Select the date, team and the agent to see the interactions for a particular agent.
Once a user is deactivated, his/her records will no longer be available on device tracker, including any historical data.
Click on a flag to see more details about each interaction. Icon on the flag indicates the type of interaction occurred on that address (ie. Sale, No Sale, etc). Interaction addresses are marked with a flag, and the flag color is dependent on how far the agent actually was from that address, at the time of the interaction.