I think he means a way to track the time spent by other people in a location, an activity mark on a map that changes in colour and size based on the ammount of people in the area and the time they spend in that area. Tracking hotspots of activity or as the game he got the idea from a "hot map". Works great in a multiplayer game like EvE but in a single player game were npc's are rooted to their locations its pretty pointless.
Valve does studies of player activity in Half Life 2 and all source games, showing where people die most, which routes they take through a zone etc. Its quite interesting to see game metrics and compare them to how you play the game though.
well,it would only count you,if you are online and signed,it will only track you,not npc's,but i see what you are getting at.