One small startup I helped out briefly many years ago was using Linux/KDE. They had it set up so that everyone's desktop was accessible from everyone else's desktop. In Linux you usually have several desktops which are easy to switch between, and they made it so that everyone else's desktops appeared in your desktop list. There are virtual desktop products for windows too.

I don't know if they used standard software for this, or whether it was their own cobbled-together scripts with normal screen-sharing apps like vnc. I was not involved in setting it up. But it worked very well.

I recall discussing using mosix (that's how old it was) too, so we were a big beowulf cluster for compiles etc. That appealed to them, but I don't know if it was acted on after I moved on.

In this particular case it wasn't about monitoring, this was about collaboration. But you can see how such a system would appeal to managers too.

This complete lack of privacy took some getting used to, but it was super focusing. It quickly sunk in that everything you did (on your screen) was visible to everyone else, and whilst there was toleration for reading the news and so on, everyone was self-censoring themselves to apply themselves.

This was in an open-plan office, but with modern bandwidth could work well remotely.