Your friends will need to install Duo for them to be able to video call you using Duo - which sounds obvious but is worth mentioning.
Google is going after Face Time and Whats App and other video-calling apps with its own solution called Duo.
Duo is free to use and enables 1-to-1 video and voice calls.
You will need a VPN installed on your computer, and buy books using your computer only.
The Amazon can detect your location through your computer IP address.