Installing this add-on "Set Users Online" and it will strengthen the online time of member for a session. It will allow you to add an user online for the entire session activity duration. i.e the same period that you set for all your users to be online at your Acp->User Options->Online Status Timeout (minutes).By doing that, Google or other Search Tool may increase your site rankings.
You can do that on an user per user basis. To do that, when editing an user, under the Action drop down tab there is a new option added called: Set User Online. There you can add that particular user in the online list.
Once added that user will appear as Viewing forum list in the online list. And as their ip address the localhost one.You can add as many users as you like to the online list.