Idle time display

One of the people in my company has suggested that it would be useful if the pop-up when hovering over a user in the contact list indicated how long that user has been idle as opposed to just stating that they are idle. E.g. if they have been idle for 2 hours then they are probably gone, if they have been idle for 2 minutes, they may still be at their desk.

Is this possible? I tried to find the appropriate places in the source, but I had limited time and didn’'t learn enough to evaluate whether It would be a quick thing that I could try patching or not.