Mutli-device support on WhatsApp coming soon: you will no longer need your phone nearby to chat0
You will no longer need your phone nearby when you're using WhatsApp on another device
The condition to have the smartphone around when using WhatsApp on another synced device is related to the end-to-end encryption the chat service provides to users. However, with the new multi-device support WhatsApp is working on, this is going to change.
You will be able to have up to four other devices connected to your WhatsApp account (not phones, though), and each one of them will have its own identity key for the end-to-end encryption. Right now, each user has only one identity key, responsible for the end-to-end encryption feature, and it is stored on the phone.
With the multi-device support, WhatsApp has also developed features to prevent eavesdropping and malicious users adding devices to someone's account. Additionally, the number of times people should verify their identity on WhatsApp will also be minimized.
You will be able to have control over devices, connected to your account.
WhatsApp has also planned an end-to-end encryption support for voice and video calls for the mutli-device beta. It's important to note that this change will not affect the way WhatsApp handles cloud backups.
Secure chat app Signal also requires a smartphone so its desktop app can send and receive messages. However, Apple has found the way of handling mutli-device end-to-end encryption as iMessage supports it.
Once the beta tests are done, the feature should be getting its official public release. At this time, thought, a release date has not been officially announced yet.