What about rendering heat-maps client-side using transparent canvas? Projects like this one and gheat (http://code.google.com/p/gheat/ http://code.google.com/p/

What about rendering heat-maps client-side using transparent canvas? Projects like this one and gheat (http://code.google.com/p/gheat/ http://code.google.com/p/gheat/) are great, but running tile-servers is a bit of a hassle...