The ability when using the web client to send a message to the person already logged in, in the case that you need to take control and aren't able to contact them by any other means.
I would welcome this feature, many of my clients have users who are LogMeIn remote home workers in their own right.
The ability for me to signal them to request I take remote control of their machine when they are still logged in and sent a ticket to me for remote help would be helpful so that they dont just get disconnected without warning.