Hah, it's not just chilling behind the screen, acting like you're doing something. There are lot of metrics which can clearly see if a developer is slacking too much but also if he's producting a lot of code which is actually bad and leads to many bugs + lost time in the future while fixing them. Since all programers' work is in digital form, it's very easy to track it down and see how an individual is doing..I actually find it abit stressfull but what can you do :)
How's it in another jobs? Is the productivity of employees being tracked as well?