serial number & Password
As an option to existing contacts lists etc, Alexa (especially Echo Show) be set up for an "access password"
This is separate to user password. Any user with both serial number and access password can vieo call to device (i.e. echo show). This would mean that families can exchange Serial Numbers and Access Passwords and instantly videocall the devices which have exchanged serial numbers and passwords. User can change Password at any time tto kill all existing permissions witth Access Password.