I've just tried the new Cartographer_HeatMap addon, and noticed that it cause my WoW client to crash. Sometimes it just locks and I have to force kill it. Other times it quits by itself and causes the WoW Error Reporting tool to appear. So, for the time being I'm disabling it.
Funny thing though is: I still have no idea what it does. :D
It appeared out of nowhere directly here: http://files.wowace.com/Cartographer_HeatMap/. Since the description isn't very informative I tried it to discover what it does, but on my WoW the only effect are systematic crashes. :)
It throw some errors on load but works for me after that. It make yellow squares on the map where I have been lately. I think there is a different tone or gets more red if you spend more time in the same spot or something like that. Not sure because i didn't want it so i deleted it.