If you already have the Netgear WiDi box then you just need to search for a compatible processor with Intel HD Graphics.
For compatible processors hit this link: http://ark.intel.com.
Between the new 3rd Generation Core processors and the 2nd Generation Core, there are about 50 processors that are WiDi-compatible with Intel HD Graphics.
If you can, I'd try to shoot for something in 3rd Generation Core. The new HD Graphics 4000 are more powerful than HD Graphics 3000 and you're likely to get a better experience with the newer chipset.
Douwe, rather than trying to figure out which individual components will support WiDi, why not just find one with a WiDi logo?
Also, here's hardware requirements for Intel's WiDi: Intel� Wireless Display — System requirements for the Intel� Wireless Display
Tips: There's two variants of WiDi. The first one generation came with 1st generation Core, and the second one, with 2nd generation Core. You'd want to check to see which version your Netgear adapter supports. Or you can tell us the model number of the Netgear device and we can tell you.
BTW, the 2nd Generation Core's WiDi is much better and that's the one you want to get. 3rd Generation Core is even better but the 2nd generation is the minimum you should get.
Some manufacturers may choose not to support WiDi despite meeting the requirements. Make sure that it does.