As far as I know, there aren't any PC monitors that do frame interpolation like some HDTV models can.
Most monitors are only 60Hz as well.
However, there is an alternative that I myself use with my 120Hz monitor.
That is using a program called "Smooth Video Project". It requires a LOT of processing power to do the more advanced frame interpolation to 60Hz, and even more for 120Hz. (Assuming 1080p video) But if you have the CPU power, it works great.