Yeah, I know. You wouldn't be able to point the laser at the core obviously, only the base of the waterblock or the heatsink. You could also check the inlet and outlet temp of the rad, inlet and outlet on the w/b, the hard drive, on some cases behind the mobo, the pump etc. I think it's useful to give you a quick reading, in case your diagnosing a coooling problem with your system.
I answered that one for you BigBen. You can tackle the inaccuracies now.
