There’s really little difference between the requirements of a remote ID system already built into a drone vs the requirements of a separate add on remote ID device. Here’s a reminder:
The Remote ID shall work in realtime and with direct periodic broadcast (using open and documented protocol that can be received directly by existing mobile devices within range) of the following:
the UAS operator registration number
ANSI/CTA-2063 serial number
the geographical position and height above the surface or take-off point
true course and ground speed
the geographical position of the remote pilot or, if not available, the take-off point;
It shall also prevent user from modifying last 4 bullets above.
The following is the key difference, a remote Add on should have a user manual with transmission protocol details and instructions to:
Install on the drone
change operator registration number
Small Print: These posts are a summary only, include my personal interpretation and are not intended to be a replacement for reading the actual rules.