+2 SMC Fan Control, may not offer the same depth of reading`s Temperature Monitor or iStat offer, what it does do extremely effectively is allow manual increase of the system cooling, monitor CPU temp & Fan RPM.
You can create profiles for battery, mains, charging. I increase base fan speed to 3000 for charging as this offsets the heat generated by the battery.
"smcFanControl is just an application. So after downloading, and unzipping it, drag it to wherever you want (e.g. the Application Folder). To uninstall it, just drag it into the trash. smcFanControl installs no permanent background processes or daemons. All changes smcFanControl does to the fan controlling get lost after you shutdown your computer (power off, not restart) or enter standby mode (as far as you don't have smcFanControl running) . Minimum fan speed then falls back to the system defaults values."
I have used smc Fan Control for several years without issue; the software has helped to cool and keep my 2.4Ghz Penryn 4.1 MacBook Pro running nonstop since 08, if I know that I am going to push the machine I can choose to intervene and increase fan speed. It`s harder to cool a hot system down, than prevent the heat build up in the first place, and anyone with a Penryn 4.1 will tell you these are hot machines, you wont be using one of these on your lap

not at 76C CPU and the case at over 40C in comparison my 13 inch i5 Air is an "iceberg"

and smc Fan Control works equally flawlessly with Lion.
Most other software packages are just monitors and albeit they offer great depth, they will not help you to cool the system or prevent heat build up. I would rather save the CPU cycles for something I can really use, and truth be known six months down the line 90% wont give a jot about the system temp
