I accidentally discovered a key feature of Relay especially if you plan to use only one device for a child with adults using the Smartphone apps. I was concerned that my child had no way to reach an adult if they didn’t also have a Relay device because the smartphone app must be open and active to respond to messages. However, if the child PRESSES AND HOLDS the VOLUME button it sends a push notification to the connected smartphones alerting you to open the app and check in with the child. This is a crucial feature that seems to be undocumented because I didn’t find any instructions about this capability. This was a make-or-break feature for us so I’m glad I accidentally found it attempting to turn off the Relay using the volume instead of the power button.