Is there such an application? One that doesn't need to poll X amounts per second and stress the CPU?
Oh, and perhaps it's best at the same time to ask if a freeware alternative exists...
(Tried DiskSpy, but even the readme warns about CPU hogging on laptops.)
EDIT: Saw that this MenuMeters thing also polls and consumes CPU time, so I guess I need an application built on a hack or .kext then, which can intercept/receive messages instead of poll for them.