Team tracking is a new feature for the Earthmate app on Apple iOS and Android. It allows an app user to see other inReach users from the Earthmate app. This will allow you to keep track of your teamates while also being in the field yourself.
This feature is currently only available for inReach Enterprise users.
Please note that you must read this document from beginning to end in order to understand how the feature works and to understand the data costs that are involved as well.