I've got this running on my desktop and my CPU temperature seems to fluctuate between 48 C in the early mornings to 59.2 C midday and evening. These computers have built in temperature monitors and are able to use this freeware.
Power Macintosh G4 (Mirrored Drive Doors)
Power Macintosh G4 (FW 800)
Power Macintosh G5
PowerBook G4 (12-inch)
PowerBook G4 (15-inch FW800)
PowerBook G4 (17-inch)
XServe
XServe (Slot loading)
http://www.bresink.com/osx/TemperatureMonitor.html
Power Macintosh G4 (Mirrored Drive Doors)
Power Macintosh G4 (FW 800)
Power Macintosh G5
PowerBook G4 (12-inch)
PowerBook G4 (15-inch FW800)
PowerBook G4 (17-inch)
XServe
XServe (Slot loading)
http://www.bresink.com/osx/TemperatureMonitor.html