Do you know of a software where it can 'broadcast' the activities of a particular user? Kind of like VNC but the viewing administrator can view multiple users, possibly in separate windows??
You can connect to as many computers as you want over VNC and simultaneously ...
A few years ago I used RAdmin for this kind of activity (http://www.radmin.com/). It's commercial, but it's pretty good, at leas it was in the time of Windows 2000/XP. They have a 30 days trial/demo, so you can try it out.
If you want a centralized hardware/software monitoring solution, and not to see what others do and spy on their screen, you may be interested in Zabbix (http://www.zabbix.com/)