Scry

Scry tells you where your colleagues are, without you having to leave your desk and its IP connectivity over the LAN ensures you know the status of home workers or users in remote offices too. Select from a list of predefined statuses including available or in a meeting or create your own specific to your organization. Scry even detects when your screen saver is active or your workstation is idle or locked and updates your status accordingly. Version 5 may include unspecified updates, enhancements, or bug fixes.

Limitations:

5-user trial