The Heads Up Display (HUD) plug-in is used to connect ATAK to HUD devices. The plug-in allows the user to set filters to specify what data should be transmitted to the HUD. Navigational routes may also be transmitted to the HUD. The plug-in provides a start "Sync" button to send data to the HUD, based on the user filters.
Currently, only the ECOTI (Clip on Thermal Imager) from Optics1 is supported by this plug-in. Map markers are sent as Cursor on Target (CoT) and routes are sent as GPX files. The user filters are stored locally in ATAK and in the ECOTI so that filters may continue to be applied if the HUD becomes disconnected from ATAK. The current ECOTI transport layer is micro-USB with data packaged per the ECOTI Interface Control Document (ICD).
UPDATE: The HUD plugin has been forked more than once and not renamed. There are separate versions of HUD that function with these hardware platforms: