Found the link...
http://www.islayer.net/index.php?id=43
Temperature & Fan support in iStat Pro and iStat nano
June 3rd, 2006
We get alot of emails asking about support for intel based macs in iStat Pro and iStat nano.
At this stage there is no support for fan or temperature sensors in Intel based Macs in either widget.
We will add support for cpu temps via the SpeedIt kernel extension in the next round of updates.
We also get alot of emails about problems with fans on some powerbooks not being reported properly and some G4 systems not reporting any sensors or fans.We are aware of both of these issues and we plan to fix the fan issue on G4 powerbooks soon. Not all G4 systems have temperature on fan sensors so if your not seeing any reported then its likely because there are none.
We appreciate people letting us know about these bugs and feature requests.
Unfortunately we simply cant reply to all the emails we get due to lack of time so if you don't hear back from us don't take it personally.
Look out for iStat Pro 3.0 in the next 2 weeks.It will be a complete rewrite and will include atleast one new and totally different style skin.
We also have version 2.0 of iStat.app due soon and we think everyone will really enjoy this one