How do I know if more than one smartphone is connected to my device?
Only the user who has been paired to the monitor (the home administrator) can invite other users to the same home. The user management is available from Settings > My home > Users. Here you can view all users invited to your home and, if desired, delete them so that they no longer have access to your home.
If there are changes to the administrator user, he/she will be notified by mail. Users will also be notified if someone logs in with the same account on another smartphone.