The results of work over the hours put in.
It also relates to the the idea of saying whether you're working or not. If you're producing great results, it shouldn't matter when/how/how much time it takes you to do it (provided maybe people can get ahold of you in an emergency). But I also seems like the key to this working is being willing to get rid of people that aren't meeting that high bar (whether weren't up to snuff or weren't because they weren't putting in enough time).
I think most organizations are unwilling/uncomfortable holding people to this high of standard on outputs, and so measure inputs (40 hours, at least not looking like you're slacking off) instead.
Charlie Munger tells a story about Fedex and how they needed to move all their packages around different planes every night in one central location. They had a team of workers to do it, but they were having trouble getting the work finished on time and keeping people motivated.
Eventually they decided -- instead of paying people by the hour -- to just pay them the same thing no matter how long it took (per shift), and let everyone go home when they were done. Lo and behold the night teams got their packages moved around much faster and and made just as much money and Fedex was able to deliver better and quicker everyone was happy.