Interesting demo, I did a similar one but with mouse movement: http://www.patrick-wied.at/projects/multiuser-heatmap/ but I think my server wont handle lots of users since I'm using an early version of Ajax Push Engine. nowjs seems to perform really good.
Btw: nice solution for the "too much data" for heatmap.js (at the initial heatmap rendering) issue :)
I couldn't figure out what the link was at first, because in Safari, absolutely nothing happens. I had to bring up the page in Chrome to see what it was supposed to be doing (heat marks).
Btw: nice solution for the "too much data" for heatmap.js (at the initial heatmap rendering) issue :)