I'd like to add it to rental cars when I travel
Hi, John. Welcome to the community! Technically yes, you are able to move your Automatic Pro adapter from one vehicle to another. However, once you've setup in one vehicle with your Automatic Pro adapter, that vehicle will be "forever" associated with your Automatic Pro account until you remove it, and no other Automatic account can setup with it. Compared to our 2nd Generation Automatic Adapter, Automatic Pro is car-centric rather than user-centric, so there can only be one account per Automatic Pro adapter. The intended use for Automatic Pro is for owners to keep track of all of their car's driving data regardless of who drives. For the scenario you are describing, using Automatic Pro with a rental car, it would not be a recommended use case.
John, if you do a lot of rental car travel, and would like to have the tracking data, Crash Alert service etc, you may want to use a Gen 2 adapter and original Automatic app for that. You can add and remove cars yourself in that app (you can't remove cars yourself from the Pro app) and setting up a Gen 2 on a rental car won't prevent another person from using their own Automatic in that car in the future. Don't worry, none of your data would be accessible to others who do set up their own adapter in a rental car later as it's all tied to your user account. Let me know if you have any further questions about that!