I would be offended if something like that was ever implemented where I worked. Not all work is done on computers all the time. I know at me work, there are peaks and troughs in work load, hard to make what we do consistent.

I could understand tracking the initial log on and logging of at the end of the day, similar to a time clock system. As that would be handy with payroll and for OH&S. Don't see a need for tracking every moment through the day.

I agree trust your employees and managers, or find another business to handle.
I agree with Astrid. I do alot of manual work, having discussions, meetings etc... that could impact the time spent on my PC. I also do alot of work from home, so not sure how that would be monitored?? I do my work efficiently and I would be peeved if I was impacted b/c I didn't work XZ amount of hours. I can see how employees would 'rort' the system to do be seen as doing more work. I'd look for another job if my work bought something like that in