The Chat messaging app on the watch is for Family Member group communication within a very small circle of trusted members.
Family Chat on the Angel Watch app is for registered Family Members. It allows anyone in this group to track and monitor your child, as well as make changes to the watch's settings and the Family Group itself. This group should be kept small.
To set up more Family Members for the in-app family group chat, different users would need to create their own Angel Watch app account with their own email address and scan the watch's QR Code, select their relationship to the wearer and request to register. You (as the administrator) would be notified of the connection request and be able to approve or reject it.
For everyone else, there's WhatsApp, similar to Skype. On the watch, these apps allow for communication to friends and others while they use a separate app completely, which they can download on their phones, tablets, or computers for free.
With these apps they'll be able to video call, text (which you can't do from the watch with the family chat app), send pics, and more- all secure and totally independent of any information on the Angel Watch™ app.
It's definitely worth taking advantage of that feature to avoid sharing any private information and allow communication to be restricted to only that: communication.
To set up WhatsApp, please do so on the watch itself and use the watch's phone number when registering. The verification SMS will get sent to your Angel Watch app in SMS Messages.
If you're having trouble getting this SMS, please put the watch's SIM card into your phone to receive the verification SMS and complete the WhatsApp activation on the watch over WiFi.
When registration is complete, you can put the SIM back into your watch and be sure to reboot.