Currently in use or not
LogMeIn has a feature where, as you start the process of beginning an unattended session, it will tell you if the "mouse and keyboard are currently in use" or "mouse and keyboard have been inactive for X hours and minutes' indicating whether the user is currently using the computer or if it is available for unattended support without disrupting the user.
This would be a fantastic addition to the software. I have many a time stressed out a client because I logged in and took over their system when they were in the middle of using it. What might also be nice, is if it displayed usage stats like you suggested in the unattended access menu, so we can know whether or not to connect just from looking at the list. This would prevent us from inconveniencing our clients entirely, and in this field, we are a dime-a-dozen, so making sure the client likes our work is incredibly important. Little things like not bothering them will go a long way.
This has been added to the feature enhancement request list.