Notify when specific contacts go online

CrossCompany

We support some associates who are only online for an hour or so a day and when we need to do maintenance on their computers it would be great if we could right click an offline contact and choose to 'notify me when online'. Once they get online I'd like to see a popup window that did not disappear until I dismissed it. Ideally, this would be a toggle that would be per contact. That way, we would get notified each time a contact is on until we right click and turn the option off.