It works only with Intel CPU's which has a digital thermal sensor (DTS). Works with Nehalem, Quad's, Core2Duo's and it's a big step forward from "old" Core2Duo plugin.
Unzip and copy the attached files into your RivaTuner/PlugIns/Monitoring directory and the rest should be easy. This plug-in includes Distance to TJMax for each core for those that like to keep an eye on that number.
We have a discussion thread + some screenshots active here in this forums thread.