I prefer to use
EaseMon employee monitoring software.
Yes, that is an option, though more expensive. I doubt any legal software is 100% hidden/silent however, and if you have a tech company your employees will know they are being monitored and act accordingly. Also, I do not want to monitor all my employees, only those that I actively suspect. It depends on the use case which to use, if you want to monitor 100 employees at once, use software, if you want the best monitoring for a few suspicious employees, I think this is the best method.
The situation in our experience was that between 1 in 20 to 1 in 100 employees were rotten apples, and we would use all available means to remove them because they disrupt 100 other people who want to work and be productive. We had no desire to be spying on all our employees however.