I made an object for the 'apple' library called [smc] which gives you
read access to the Apple System Management Controller (http://en.wikipedia.org/wiki/System_Management_Controller ). This allows you to get temperatures from sensors, like the CPU
temp, and also info about the fans, like speed, min, max, etc. There
are lots of other possibilities to explore.

Also, write access is possible, like to set the fan speed, but I
haven't really tested it. It needs a bit more work to be easy, but
you should be able to send byte sequences. Watch out, you could do
something stupid like turn your fan off, cooking your computer!

I have the audacity to believe that peoples everywhere can have three
meals a day for their bodies, education and culture for their minds,
and dignity, equality and freedom for their spirits. - Martin
Luther King, Jr.