Dmitriy Simushev, let us consider Skype. If we login Skype and went away. Then the Skype status will be changed as "away" after few minutes. So, that the others can identify that he is away.
In our Mibew application, if the operator opened chat window and chat with a visitor. In the meantime if the operator went away for more than "X" seconds or minutes, then we should notify the visitor that he is away. Do you need some more details.
Please help me on this.