>because the software infrastructure for measuring that doesn't exist (though I suppose someone could write it);
What the hell are you talking about? The endermen in minecraft change behavior based on whether you are looking at them or not, and minecraft has hardly a bastion of bleeding edge game engine technology. The difference between making an enderman attack if you look at it for more then 2 seconds and firing a metric if you look at a coke bottle for more than two seconds is pretty minimal.
A metric tool that sends data on how long you keep certain objects within the center of your FOV can be backed with off the shelf free software[1]. The infrastructure is commonplace, well tested and used daily for a myriad of metric related tasks all over the world.
What the hell are you talking about? The endermen in minecraft change behavior based on whether you are looking at them or not, and minecraft has hardly a bastion of bleeding edge game engine technology. The difference between making an enderman attack if you look at it for more then 2 seconds and firing a metric if you look at a coke bottle for more than two seconds is pretty minimal.
A metric tool that sends data on how long you keep certain objects within the center of your FOV can be backed with off the shelf free software[1]. The infrastructure is commonplace, well tested and used daily for a myriad of metric related tasks all over the world.
[1] http://grafana.org/