It's need specific ACPI coding and testing. Try to look in projectosx forums about ACPISensors maybe you'll found something usefull.
For those who have nVidia cards, please test latest NouveauSensors and show me your kernel log. I have ported i2c base from nouveau driver. There is no monitoring feature in it for now. I need to test how i2c base works in general before I start to port monitoring drivers.