The power of this app is to use "Google Calendar" and "Google Contacts". It isn't a new management appointments app!
With Calendar Reminder you can access your appointments stored in "Google Calendar" and add a reminder to one or more contacts of yours. You can choose the message to send and how many minutes before to send it.
Once you setted the contacts to reminder the appointment, at the specific time you'll receive a notification and simultaneily will be send a message to the chosen contacts.
Warning: you must check if this app belongs to the protected apps list in order to work properly in the background.