Extend Remote Desktop into Remote Assistance, integrate into Ubuntu Help Centre

Scenario: Alice is helping Bob to use his laptop running Ubuntu Linux. They are geographically separated, both have internet access, possibly through Network Address Translation. Alice and Bob are in near real time communication by phone or instant messaging. They know one another.

Problem: Alice must instruct Bob, in detail, without visual feedback, what to do. Bob must relay to Alice, what he sees. Both are distracted from their actual goal and frustrated by difficulty describing matters to the other.

Proposal: Somewhere prominent in the default install such as in Ubuntu Help Centre, allow Bob to request assistance, specifically from Alice. The request should include information to aid NAT traversal and may include access controls, a time/connections limit. Bob's computer should listen for a connection from Alice and ask for confirmation from Bob, when Alice attempts to connect.
Once connected Alice shall be able to watch Bob's desktop in real time and optionally share control. Bob or Alice shall be able to close the connection at will. Once a connection is closed or any time limit expires, Bob's computer shall cease listening for connections.