I just came across a new program called mcalib (hm, does this have to do something with xcalib?).
It is a calibration utility capable of calibrating monitors with the Pantone Huey colorimeter. This guy reverse-engineered the USB protocol of the Huey. Good job!
I must admit that I have no idea how good the Huey really is - but it's relatively cheap and I will probably go for one and extend my collection of colorimeters.
So far no real colorimetry is involved and mcalib only uses the video LUTs for making the display linear and so on ... But it's a good foundation and the code could be possibly integrated into ArgyllCMS.
Here's the link btw.: http://sourceforge.net/projects/mcalib